1) adds a :DiffReview command to review code changes
in the current workspace.
2) removes the need to have patchutils (specifically filterdiff)
installed on the system by implementing patch extraction in
pure vim script.
The plugin takes an 'hg export'ed patch (in fact any
single or multi file patch) and opens multiple tabs
containing vim diff/merge windows for each affected
file in the patch allowing full visual code reviews.