Highlight copied/moved lines in Differential

Summary: The color used for this feature is pretty important and I am bad with colors.

Test Plan:
View diff created by D2320 with some copied lines and one line changed:

{F10604, size=full}

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2321