Expose Rugged diff options
Fix call to Rugged::Diff#find_similar!
Remove call to `find_similar!`

`Rugged::Diff#find_similar!` is called in `Repository#diff` and
shouldn't be called again in `Diff#diffs`.
Always detect file renames

Call `Ruged::Diff#find_similar!` when generating diffs, even if the
`:break_rewrites` option is false.
Merge branch 'master' into rugged-diff-options

Conflicts:
	lib/gitlab_git/repository.rb
	spec/diff_spec.rb
Merge branch 'rugged-diff-options' into 'master'

Expose Rugged diff options

Add an argument to methods that generate a diff so that a hash of options can be passed to Rugged.  This will allow Gitlab to ignore whitespace in diffs as suggested on [feedback.gitlab.com](http://feedback.gitlab.com/forums/176466-general/suggestions/4230569-tune-diff-output-in-merge-request).

See merge request !6