Add support for custom rn-cli.config.js

[jevakallio]

Solves #7

API

The only requirements are, that the user's config needs to be called /rn-cli.config.js (in the project root), and the getBlackListRE method must take an optional array of "default" modules to blacklist, and pass those to blacklist. Something like:

const blacklist = require('react-native/packager/blacklist');

module.exports = {
  getBlacklistRE(defaults = []) {
    const modulesToBlacklist = [
      /* ... your deps */
    ];

    return blacklist(defaults.concat(modulesToBlacklist));
  }
};

All the other custom config methods are passed through and should work unmodified.

Testing notes

The easiest way to test this is:

git clone git@github.com:FormidableLabs/whackage.git
git checkout feature/support-custom-rn-cli.js
npm install
npm link

And in your own project:

npm link whackage

[parshap]

Tested and this is working great!