Update babel-preset-minify dependency

[nemophrost]

Some great fixes and improvements have made it into babel-preset-minify and neutrino could benefit greatly from them.

[nemophrost]

Any word on this? Right now you can't set any minify plugin options for plugins disabled by default.

[eliperelman]

Seems pretty innocuous, thoughts @edmorley?

[edmorley]

There are a few more changes than this upstream:
master...webpack-contrib:master

Also worth noting that upstream is still on 0.3.0, whereas this PR updates to 0.4.0 which has even more breaking changes:
https://github.com/babel/minify/blob/master/CHANGELOG.md

Neutrino 9 stops using this plugin, so any changes here would only be useful for Neutrino 8, where breaking changes are not possible (with the caveat that I haven't looked at how severe the breaking changes are; they might not affect us / might still be worth it if the minification bug fixes are important enough).