Use git-utils module

Removes the need to include libgit2 as this is now handled by the
git-utils module which provides functions that were previously in
git.mm and git.coffee

package.json

@@ -7,7 +7,7 @@
     "ctags": "0.1.0",
     "oniguruma": "0.4.0",
     "mkdirp": "0.3.5",
-    "git-utils": "0.1.0"
+    "git-utils": "0.2.0"
   },
 
   "scripts": {