Update:

 - only change is to make the regexp for hunting out binary changes is now a class member variable

================================================================

Update:

These changes preserve the same behaviour of the previous functional approach to diff parsing, it just wraps it all in a class.

 - removed useless whitespace
 - compiled binary-change-matching regexp in __init__

================================================================

Update:

Split diff parsing into smaller methods, makes it easier to tweak per SCM implementation

================================================================

I have split this review request from the GitTool in http://reviews.review-board.org/r/80/

This patch will create a DiffParser class to allow SCMTool's to override the diff parsing operation, and (hopefully) lead to less code duplication. It is pretty much just jamming the previous functional approach into a class.  

Unittests updated, tests pass