guidelines / how-to for contributing

[lmccart]

[kadamwhite]

This should probably include at minimum

• style guide
• commenting guide, e.g. an example YUIDoc block
• expectations for unit test coverage and/or an explanation of how to add unit tests

imo PR contributions without tests should get flagged with a github issues tag, e.g. needs-tests, so that we can help walk less experienced devs through the process of adding and running tests for their patches

[lmccart]

also, some information about how to get involved, ie contact email and possibilities for things to work on (this is more or less covered by github issues)