Update to Traceur 0.52

Using the old 0.45 was causing tests to break in Travis.
Merge pull request #226 from matthewp/traceur-52

Update to Traceur 0.52
When loading a main bundle in production mode, use the full pathname instead of truncating to the filename, to be able to uniquely reference different mains that may have the same filename. e.g. `users/list.js` and `tasks/list.js`. This is the corresponding change to the steal-tools PR: https://github.com/bitovi/steal-tools/pull/54