Upgrade to Webpack 3 with module concatenation

[nolanlawson]

This reduces the size of application.js from 670196 bytes to 655404 bytes (14.8kB saved). The other bundles are roughly the same size as before.

You can read more about how module concatenation (aka scope hoisting) works here. Essentially this will just take all of our modules inside of application.js and squash them into a single function scope instead of having multiple function(){} wrappers around each one. It de-penalizes us for having multiple small modules.

Interestingly this actually increases the gzip size of application.js slightly (171181 to 173646, 2.46kB) but I think the tradeoff is worth it given that the ungzipped size is what the browser has to parse, and less JS to parse is always good.

[nolanlawson]

/cc @sorin-davidoi

[sorin-davidoi]

Nice! Love it that we have all our dependencies up-to-date and can take advantage of new features almost right away!

[sorin-davidoi]

Appears to break webpack-dev-server: webpack/webpack-dev-server#947

[nolanlawson]

Hm should we roll back or can we just fork webpack-dev-server until they fix it? From the discussion, sounds like it's a fairly easy fix on their end.

[sorin-davidoi]

I don't mind fixing it locally but other people might run into trouble. There is a PR open to fix it webpack/webpack-dev-server#946, hope they merge it soon.

[nolanlawson]

In that case we can just change our dependency in package.json to "webpack-dev-server": "lencioni/webpack-dev-server#patch-1" while we wait for a fix.