Replaces Ace with CodeMirror.
This adds support for editing on iOS and Android.
Improves CodeMirror options and upgrades to latest CM head.
Introduces new responsive theme for the Playground.
Fixes gh-55.
Merge branch 'codemirror'

* codemirror:
  Introduces new responsive theme for the Playground.
  Improves CodeMirror options and upgrades to latest CM head.
  Replaces Ace with CodeMirror. This adds support for editing on iOS and Android.