Moved contributing out of readme into file recognized by github issues

What do you think about moving the info from readme to a contributing file? When you try to open an issue it will ask you to review the guidelines and is helpful. Many large projects use this to deter not researching duplicate issues and enforcing coding standards.

You can read about it on the [GitHub help](https://help.github.com/articles/how-do-i-set-up-guidelines-for-contributors) and the [GitHub blog](https://github.com/blog/1184-contributing-guidelines).