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.
"checks it out" is a euphemism. I would say:

As an external user:
* I can clearly identify the state of a contribution
* I can comment and provide feedback on the contribution

As a Chef maintainer:
* I can see the list of contributions requiring review
* I can see the list of bug reports requiring investigation