Assetmanager commits for work around to prevent build errors / convert tests to coffee

See commits for changes. The tables tests are no longer passing with using Ember in test mode. Also the random compile error when running the build seems to be an issue with tmp files see: http://stackoverflow.com/questions/12866054/uninitialized-constant-rakepipelinemanifestentrydatetime so I added the work around in the Assetfile.

Also added the watcher to compile the coffee tests after saving edits to the files in the js directory.