Add option babelifyDeps

[aknuds1]

Choose one: This is a 🙋 feature

I add the option babelifyDeps to control whether the scripts method applies the babelify transform to dependencies or not. I need this since calling Babel on my dependency tree slows down my build by about 5-6 times and at least one of my dependencies (underscore.js) also breaks from this.

Note: I'm still unsure whether babelifyDeps should be true by default, since it's an intrusive feature that easily breaks or simply slows down your build significantly. Personally I would have it off by default.

Checklist

• tests pass
• tests and/or benchmarks are included
• documentation is changed or added

Context

See #423.

Semver Changes

I would recommend a minor version upgrade, since this adds an option.

[goto-bus-stop]

IMO we should remove it entirely in 10.0 … or figure out a way to make it only compile stuff that is not ES5 compatible (maybe with https://www.npmjs.com/package/is-es-version and aggressive caching), or do a dual bundle thing—one with modern syntax and one with ES5.

In the mean time this is probably a reasonable compromise even though it adds an option.

[goto-bus-stop]

will merge both this and #455 soon then and release as minor