Kinda start bridging data in from GitHub via Nuance

Summary: Ref T10538. Very sloppy, but starting to sort of work. This sort of gets a piece of framework into a reasonable spot, next couple of diffs are going to be "extract comment text" and "show stuff in the UI" sorts of things.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10538

Differential Revision: https://secure.phabricator.com/D15511