Use uglifyjs-webpack-plugin ^1.0.1 to optimize the supervisor code

[pcarranzav]

We've been using UglifyJS 0.4.6 (the webpack default) so far, but this doesn't support ES6 and some dependency
updates are starting to cause builds to break (e.g. request/request#2772, which also happens to break
my builds in the multicontainer branch).

Here we switch to the latest uglifyjs-webpack-plugin which is designed for ES2015 support.

Change-Type: patch
Signed-off-by: Pablo Carranza Velez pablo@resin.io

Edited: originally this PR meant to use babel-minify instead of the newer uglifyjs, hence Page's comments below.

[Page-]

Is there any reason you didn't use 1.x of uglifyjs-webpack-plugin? That should support uglify-es: https://github.com/webpack-contrib/uglifyjs-webpack-plugin/blob/master/CHANGELOG.md

[pcarranzav]

@Page- webpack by default depends on uglifyjs-webpack-plugin ^0.4.6, so to be able to use the newer one we'd have to use a forked webpack. See: webpack/webpack#3673

[Page-]

I'm pretty sure you can do it by adding the 1.x version to package.json and using the plugin via

var UglifyJSPlugin = require('uglifyjs-webpack-plugin')
...
plugins: [
	...
	new UglifyJSPlugin()
]

Mainly I'm just wondering if uglifyjs will give better results, and it should also hopefully be closer to what we currently do

[pcarranzav]

@Page- thanks, that worked! I had tried it before and it hadn't worked but I guess I must've done something wrong.