[First Step] implement transform function for .babelrc.js

[hiroppy]

This is the first step for replacing .babelrc.js:)

Currently, it is possible to replace arrays without nests. Next, we have to deal with the following

  presets: [['babel-preset-env', {
    "browsers": ["last 2 versions", "safari >= 7"]
  }]]

[hzoo]

Nice start!

However I don't think replacing .babelrc.js is much of a priority for us (at least for Babel v7, it will be plenty useful in the future). You can only use that file in v7 alpha so this would only be useful for people changing from alpha to beta, and most people will be upgrading their .babelrc

[hiroppy]

@hzoo That’s true. I agree with you:) Ok, we'll merge only this PR and let's do another task:smile:

[hiroppy]

probably related #49