Remove unicode regexp support and reduce50%+ bundle size.

[ksenginew]

I had recently inspected buble dependencies with bundlephobia.com
https://bundlephobia.com/package/buble@0.20.0

regenerate-unicode-properties package takes 47% of the bundle size. It's a dependency of regexpu-core.

regexpu core enables rewriting regular expressions that make use of the ES6 u flag into equivalent ES5-compatible regular expression patterns.

So regepu-core uses 50%(47%+3%) of the bundle size for just unicode regular expressions with cavets
That's not an essential feature. buble can remove support for unicode regular expressions or create a new bundle(named babel-lite or something) without unicode regexp support