Upgrade Scala.js to 0.5.4, fixes PhantomJS polyfill issue.

μTest also upgraded to 0.2.3.
Refactor: Internal
Next version will be 0.5.0
Refactor: ReactComponentB
Refactor: ReactComponentC
Refactor: ReactComponent{B,C}
Merge branch 'types'
Merge branch 'master' of github.com:japgolly/scalajs-react