Added tox.ini to run tests with python2/3, and CONTRIBUTING based on …

…datalad's, and added contextlib2 for vcr.py to requirements.txt

CONTRIBUTING.md

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+Contributing to DueCredit
+=========================
+
+**Note: This document is just to get started, more thorough
+contributing guidelines are coming.**
+
+[gh-duecredit]: http://github.com/duecredit/duecredit
+
+Files organization
+------------------
+
+- `duecredit/` is the main Python module where major development is happening,
+  with major submodules being:
+    - `cmdline/` contains commands for the command line interface.  See any of
+      the `cmd_*.py` files here for an example
+    - `tests/` all unit- and regression- tests
+        - `utils.py` provides convenience helpers used by unit-tests such as
+          `@with_tree`, `@serve_path_via_http` and other decorators
+- `tools/` might contain helper utilities used during development, testing, and
+  benchmarking of DueCredit.  Implemented in any most appropriate language
+  (Python, bash, etc.)
+
+How to contribute
+-----------------
+
+The preferred way to contribute to the DueCredit code base is 
+to fork the [main repository][gh-duecredit] on GitHub.  Here
+we outline the workflow used by the developers:
+
+
+0. Have a clone of our main [project repository][gh-duecredit] as `origin`
+   remote in your git:
+
+          git clone --recursive git://github.com/duecredit/duecredit
+
+    `--recursive` is used to initialize any needed git submodules.  If you have 
+    cloned without it already, just run `git submodule update --init --recursive`
+
+1. Fork the [project repository][gh-duecredit]: click on the 'Fork'
+   button near the top of the page.  This creates a copy of the code
+   base under your account on the GitHub server.
+
+2. Add your forked clone as a remote to the local clone you already have on your 
+   local disk:
+
+          git remote add gh-YourLogin git@github.com:YourLogin/duecredit.git
+          git fetch gh-YourLogin
+
+    To ease addition of other github repositories as remotes, here is
+    a little bash function/script to add to your `~/.bashrc`:
+
+        ghremote () {
+                url="$1"
+                proj=${url##*/}
+                url_=${url%/*}
+                login=${url_##*/}
+                git remote add gh-$login $url
+                git fetch gh-$login
+        }
+
+    thus you could simply run:
+
+         ghremote git@github.com:YourLogin/duecredit.git
+
+    to add the above `gh-YourLogin` remote.
+
+3. Create a branch (generally off the `origin/master`) to hold your changes:
+
+          git checkout -b nf-my-feature
+
+    and start making changes. Ideally, use a prefix signaling the purpose of the
+    branch
+    - `nf-` for new features
+    - `bf-` for bug fixes
+    - `rf-` for refactoring
+    - `doc-` for documentation contributions (including in the code docstrings).
+    We recommend to not work in the ``master`` branch!
+
+4. Work on this copy on your computer using Git to do the version control. When
+   you're done editing, do:
+
+          git add modified_files
+          git commit
+
+   to record your changes in Git.  Ideally, prefix your commit messages with the
+   `NF`, `BF`, `RF`, `DOC` similar to the branch name prefixes, but you could 
+   also use `TST` for commits concerned solely with tests, and `BK` to signal
+   that the commit causes a breakage (e.g. of tests) at that point.  Multiple
+   entries could be listed joined with a `+` (e.g. `rf+doc-`).  See `git log` for 
+   examples.  If a commit closes an existing DueCredit issue, then add to the end 
+   of the mesage `(Closes #ISSUE_NUMER)`
+
+5. Push to GitHub with:
+
+          git push -u gh-YourLogin nf-my-feature
+
+   Finally, go to the web page of your fork of the DueCredit repo, and click
+   'Pull request' (PR) to send your changes to the maintainers for review. This
+   will send an email to the committers.  You can commit new changes to this branch
+   and keep pushing to your remote -- github automagically adds them to your
+   previously opened PR.
+
+(If any of the above seems like magic to you, then look up the
+[Git documentation](http://git-scm.com/documentation) on the web.)
+
+
+Quality Assurance
+-----------------
+
+It is recommended to check that your contribution complies with the following
+rules before submitting a pull request:
+
+- All public methods should have informative docstrings with sample usage
+  presented as doctests when appropriate.
+
+- All other tests pass when everything is rebuilt from scratch.
+
+- New code should be accompanied by tests.
+
+
+### Tests
+
+All tests are available under `duecredit/tests`.  To execute tests, the codebase
+needs to be "installed" in order to generate scripts for the entry points.  For 
+that, the recommended course of action is to use `virtualenv`, e.g.
+
+```sh
+
+virtualenv --system-site-packages venv-tests
+source venv-tests/bin/activate
+pip install -r requirements.txt
+python setup.py develop
+```
+
+On Debian-based systems you might need to install some C-libraries to guarantee
+installation (building) of some Python modules we use.  So for `lxml` please first
+
+```sh
+
+sudo apt-get install libxml2-dev libxslt1-dev
+```
+
+Then use that virtual environment to run the tests, via
+
+```sh
+python -m nose -s -v duecredit
+```
+
+or similiarly,
+
+```sh
+nosetests -s -v duecredit
+```
+
+then to later deactivate the virtualenv just simply enter 
+
+```sh
+deactivate
+```
+
+Remember, some tests use testing repositories which are available as submodules
+under the `duecredit/tests/testrepos` submodule (two tier- to not pollute
+top repository submodules namespace).  To enable those tests do:
+
+```sh
+git submodule update --init --recursive
+```
+
+or do the original repository clone described above with the `--recursive` 
+option.
+
+
+### Coverage
+
+You can also check for common programming errors with the following tools:
+
+- Code with good unittest coverage (at least 80%), check with:
+
+          pip install nose coverage
+          nosetests --with-coverage path/to/tests_for_package
+
+
+### Linting
+
+We are not (yet) fully PEP8 compliant, so please use these tools as
+guidelines for your contributions, but not to PEP8 entire code
+base.
+
+[beyond-pep8]: https://www.youtube.com/watch?v=wf-BqAjZb8M
+
+*Sidenote*: watch [Raymond Hettinger - Beyond PEP 8][beyond-pep8]
+
+- No pyflakes warnings, check with:
+
+           pip install pyflakes
+           pyflakes path/to/module.py
+
+- No PEP8 warnings, check with:
+
+           pip install pep8
+           pep8 path/to/module.py
+
+- AutoPEP8 can help you fix some of the easy redundant errors:
+
+           pip install autopep8
+           autopep8 path/to/pep8.py
+
+Also, some team developers use
+[PyCharm community edition](https://www.jetbrains.com/pycharm) which
+provides built-in PEP8 checker and handy tools such as smart
+splits/joins making it easier to maintain code following the PEP8
+recommendations.  NeuroDebian provides `pycharm-community-sloppy`
+package to ease pycharm installation even further.
+
+
+Easy Issues
+-----------
+
+A great way to start contributing to DueCredit is to pick an item from the list of
+[Easy issues](https://github.com/duecredit/duecredit/labels/easy) in the issue
+tracker.  Resolving these issues allows you to start contributing to the project
+without much prior knowledge.  Your assistance in this area will be greatly
+appreciated by the more experienced developers as it helps free up their time to
+concentrate on other issues.

requirements.txt

@@ -1,5 +1,6 @@
 mock
 nose>=1.3.4
 vcrpy
+contextlib2
 requests
 citeproc-py

tox.ini

@@ -0,0 +1,27 @@
+[tox]
+envlist = py2,py3
+#,flake8
+
+[testenv]
+commands = nosetests {posargs}
+deps = -r{toxinidir}/requirements.txt
+
+[testenv:cover]
+commands = nosetests --with-coverage {posargs}
+
+[testenv:flake8]
+commands = flake8 {posargs}
+
+[testenv:venv]
+commands = {posargs}
+
+[flake8]
+#show-source = True
+# E265 = comment blocks like @{ section, which it can't handle
+# E266 = too many leading '#' for block comment
+# E731 = do not assign a lambda expression, use a def
+# W293 = Blank line contains whitespace
+#ignore = E265,W293,E266,E731
+max-line-length = 120
+include = duecredit
+exclude = .tox,.venv,venv-debug,build,dist,doc,git/ext/