Summary: introducing a new friend called DifferentialHunkParser. Sort of like the DifferentialChangesetParser but works with hunks only. tried to grab hunk parsing type things from across the code base and move them into this new class.
Test Plan: unit tests and played around in Differential a bit.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2009
Differential Revision: https://secure.phabricator.com/D4351
