Add ignore white space option in merge request diff
Created by: yms9654
fix this issue(https://gitlab.com/gitlab-org/gitlab-ce/issues/1393). It supports a ?w=1 option on the URL when viewing diffs.
When I call reload_content method on MergreRequsetDiff, it change state to :collected. But collected? method return false.. So I add a collected? method on MergeRequestDiff class.