Switch to webpack workflow

A set of changes to match Blip and Clamshell's front-end workflow with Webpack.

@cheddar Do you want to take a look and tell me what you think? Thanks!
Yeah, it's a race condition, so it's very possible that you haven't seen it yet.  It can take a while for the infinite loops to happen.  It's a race condition in how shelljs converts asynchronaiety in node.js to synchronous exec calls:

https://github.com/arturadib/shelljs/issues/51

It's not actually fixable.  If we are going to use shelljs, then we should definitely have a note to people indicating that this can happen.