Support babel transform options

Babel has many transform options.

• Options · Babel

espower-babel support babel transform options with .babelrc

espower-babel read ${cwd}/.babelrc if exists.

also can manually configure babel transform options.

require('espower-babel')({
    babelrc: {
        experimental: true
    }
})

• add babel transpiling options support #3

Thanks @mohayonao

---

use case

• JavaScript - ES7 の Async/Await を使ってみた - Qiita