GitHub Issues Workflow for Chef

This RFC codifies the workflow of Chef maintainers while maintaining issues and contributions for Chef.

Special thanks to @btm / @lamont-granquist / @danielsdeleo / @mcquin / @adamedx / @jdmundrawala  who has helped put the first version come together.
git itself supports this with -a and -s options to `git am`, but I don't know if any github workflow becuase github inherently doesn't understand "approval" (this is something I like about Phabricator). That said, github loves feature requests (or so they tell me at conferences), so perhaps we should request something like this?