Add a contributing file

contributing.md

+#Contributing
+This project follows the normal github workflow.
+
+#Working on a feature or issue
+* Please make a fork of the repository if you do not already have one.
+* Create a branch for the feature/issue with a name like `feature-x` or `issue-#`.
+* Commit your changes to that branch.
+* Create a pull request with your changes.