Add best practices for contributions

Author: tmrts

CONTRIBUTING.md

@@ -0,0 +1,47 @@
+How to Contribute to aima-python
+==========================
+
+Thanks for considering contributing to aima-python.
+
+Contributing a Patch
+====================
+
+1. Submit an issue describing your proposed change to the repo in question.
+1. The repo owner will respond to your issue promptly.
+1. Fork the desired repo, develop and test your code changes.
+1. Submit a pull request.
+
+Reporting Issues
+================
+
+- Under which versions of Python does this happen?
+
+- Is anybody working on this?
+
+Patch Rules
+===========
+
+- Ensure that the patch is python 3.5 compliant.
+
+- Include tests if your patch is supposed to solve a bug, and explain
+  clearly under which circumstances the bug happens. Make sure the test fails
+  without your patch.
+
+- Try to follow `PEP8 <http://legacy.python.org/dev/peps/pep-0008/>`_, but you
+  may ignore the line-length-limit if following it would make the code uglier.
+
+Running the Test-Suite
+=====================
+
+The minimal requirement for running the testsuite is ``py.test``.  You can
+install it with::
+
+    pip install pytest
+
+Clone this repository::
+
+    git clone https://github.com/aimacode/aima-python.git
+
+Then you can run the testsuite with::
+
+    py.test