New flow to retain all of the other folders within public/assets

The new flow:

* Copy all of `public/assets` into `public/assets-ugly` (4 to 7 second perf hit)
* Do an in-place, parallel uglification of `public/assets-ugly/js`
* Do an rjs build from `public/assets-ugly` into `public/assets-built`
 * Cannot do an inplace bundling due to conflicting `common` bundle name
* Copy the rjs built assets from `public/assets-built` back to `public/assets-ugly`
* Swap `public/assets` with `public/assets-ugly`