Use UglifyJS for minification

[tracend]

Google's Closure service was OK to implement but in production it has proven to be problematic - mostly because it's not designed to handle a lot of workload.

This error message keeps popping up:

Too many compiles performed recently. Try again later

From the looks of it it doesn't seem to be that uncommon:
https://www.google.com/search?q=google+closure+%22Too+many+compiles+performed+recently.+Try+again+later%22

To better serve the community it is best if this service is removed - instead of finding work arounds...

UglifyJS is pretty much a standard in the Node.js world and there's this project that is a lightweight application around it to use as an external service:
https://github.com/marijnh/UglifyJS-service

Using this service instead seems worth the effort.

[tracend]

Closing as addressed