diffusion: fix git log author name parsing

Summary:
The current git log parsing wouldn't work correctly when space
appeared in the author name. This diff fixes to regex to work
with multi-word author names and increases the author column
width when viewing blame info to accound for larger author names.

Test Plan:
viewed file with blame info in diffusion where author
name contained multiple words

Reviewed By: jungejason
Reviewers: jungejason, epriestley
CC: aran, rm, jungejason
Differential Revision: 399