Merge pull request #85 from jgrewe/master

first version of contribution guidelines.

Contributing.md

@@ -0,0 +1,45 @@
+How to contribute to nix
+===========================
+
+This document gives some informationa how to contribute to the pandora/nix project.
+
+
+Contributing
+------------
+
+If you want to contribute to the project please create a fork of the
+repository. When you are done implementing a new feature/fixing a bug
+please send pull requests.
+
+If you experience bugs in the library or find flaws/errors in the documentation
+please create an **issue** and tag them accordingly.
+
+
+Code style
+----------------
+
+   - We use a slightly modified K&R style in which we use 4 spaces
+   instead of tabs for indentation.
+   - Method names are written in camelCase.
+   - Getter and setter methods for properties are named
+   according to the property name (e.g. setting the name of an entity is
+   done with name(const string &name) and retrieved with name()).
+   Methods that delete entities are named with deleteXyz(). Those that
+   remove references to other entities (but do not delete) are
+   named removeXyz().
+
+   - Add Doxygen docstrings to methods.
+
+
+Interface design
+----------------
+
+
+Testing
+-------
+
+   - Unit test can be found in the test sub directory.
+   - Every implemented method must be tested.
+   - Please make sure that all tests pass before merging/sending pull
+   requests. 
+