Typeface data should end up as requires from local file

[johno]

In order to avoid duplicate data we should have a structure like:

{
  // ...
  typefaces: {
    normal: {
      400: require('./typefaces/normal-400.json')
      // ...
    }
    // ...
  }
}

This should knock out about half the size of installed font packages, ending up in the range of 250-700kB.