Missing a CONTRIBUTING file

[PurpleBooth]

A contributing file is a place for a user to work out how to contribute to a project, and what coding standards, and things they need to do before submitting code. It is also the place you should include a code of conduct, to make sure people know they can be expected to be treated fairly by the project. https://gist.github.com/PurpleBooth/6f1ba788bf70fb501439