Updated CONTRIBUTING.md and link in README.md

CONTRIBUTING.md

@@ -0,0 +1,68 @@
+Contributing to Surprise
+========================
+
+Pull requests are always welcome! Before submitting a new pull request, please
+make sure that:
+
+* Your code is [clean](https://www.youtube.com/watch?v=wf-BqAjZb8M),
+  [pythonic](https://www.youtube.com/watch?v=OSGv2VnC0go), well commented and
+  also well documented (see below for building the docs).
+* The tests are passing. Also, write some tests for the changes you're
+  proposing. If you're not willing to write tests, it's best not to submit a PR
+  (it's just a waste of time for everyone).
+* Your code follows [PEP 8](https://www.python.org/dev/peps/pep-0008/) as much
+  as possible. Coding style is automatically checked when tests are run.
+* For new prediction algorithms or similarity metrics, please submit a
+  relevent benchmark outlining the performance of the new feature (in terms of
+  accuracy, computation time, etc.). You can take a look at
+  [`examples/benchmarks`](https://github.com/NicolasHug/Surprise/blob/master/examples/benchmark.py)
+  for inspiration.
+
+Set up
+------
+
+It's highly recommended to use a virtual environment. All the packages needed
+for the development of Surprise (sphinx, flake8, etc...) can be installed by
+running
+
+    pip install -r requirements_dev.txt
+
+Then, you can install your local copy of the repo:
+
+    pip install -e .
+
+Any change to the code should now be immediately reflected during execution. If
+you're modifying Cython code (`.pyx` files), you'll need to compile the code in
+order to see the chanes. This can be achieved by running `pip install -e .`
+again.
+
+Running and writing tests
+-------------------------
+
+Our testing tool is [pytest](http://doc.pytest.org/en/latest/). Running the tests is as
+simple as running
+
+    pytest
+
+in the root directory.
+
+For writing new tests, check out pytest getting started guide and / or take
+inspiration from the current tests in the `tests` directory.
+
+
+Building the docs locally
+-------------------------
+
+The docs can be compiled with
+
+    cd doc
+    make html
+
+You can check the results in `doc/build/html`. Please make sure that the docs
+compile without errors. Run `make clean` from time to time in order to avoid
+hidden warnings. You can check spelling mistakes by running
+
+    make spelling
+
+Legit words that are not recognized can be added in the
+`source/spelling_wordlist.txt` file.

README.md

@@ -205,7 +205,7 @@ If you'd like to see some features or algorithms implemented in
 [Surprise](http://surpriselib.com), please let us know!
 
 Please feel free to contribute (see
-[guidelines](https://github.com/NicolasHug/Surprise/blob/master/.github/CONTRIBUTING.md))
+[guidelines](https://github.com/NicolasHug/Surprise/blob/master/CONTRIBUTING.md))
 and send pull requests!
 
 For bugs, issues or questions about [Surprise](http://surpriselib.com), you can