Allow skipping assets optimization

[archdragon]

Added changes

Based on our discussion in #154 I propose using NODE_ENV to skip assets minification when necessary.

NODE_ENV=development mix dev will run webpack in development mode - in this mode minification steps are ignored.

This allows us to easily debug JS code.

Default	NODE_ENV=development

Comment/Question

Typically we would expect webpack to run in development mode by default and switch to production when necessary (ie. during deployment).

I just didn't want to mess with our current workflow - if I changed the default to development we would have to remember to always build assets in production mode before submitting them.

Or maybe it's not a big deal and I should just use development as the default env?

Resolves #150

[lukaszsamson]

I don't see how this can help debugging live_dashboard JS when live_dashboard is a dependancy. In that case the JS code is taken from priv/static and is already minified. Besides, the client application may not even use webpack at all.
In NodeJS world libraries come either not minified or minified with source maps. Why not distribute source maps here?

[josevalim]

Yes, if you want to debug it, then you need to swap to a path dependency and recompile it locally. We can add more information to the README.

[josevalim]

@lukaszsamson there is more information here on why the usual source maps approach does not work for us: #154

[lukaszsamson]

I've read the discussion in #154 and it's not evident what is the reason against providing inlined source maps? 400kB is not much for an internal administration panel (in my experience a medium sized Angular SPA easily reaches 30MB in dev mode while working smooth). Building two separate bundles for dev and prod is also an option.

[josevalim]

If you want to send a PR that builds two bundles and then used a flag to control which, we would love to take a look at it. Thanks!

[josevalim]

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