Inserting the Milestone title between quotes on GFM auto complete

This is due to the fact that for multiple word titles it might be
an invalid reference without the quotes

app/assets/javascripts/gfm_auto_complete.js.coffee

@@ -90,7 +90,7 @@ GitLab.GfmAutoComplete =
       alias: 'milestones'
       searchKey: 'search'
       displayTpl: @Milestones.template
-      insertTpl: '${atwho-at}${title}'
+      insertTpl: '${atwho-at}"${title}"'
       callbacks:
         beforeSave: (milestones) ->
           $.map milestones, (m) ->