Replaced the bundled version of tinymce with 4.1.2.
Updated the latest version of TinyMCE, v4.1.2.

This is potentially unstable. I've tested in a vanilla Rails 3 app,
and the combined javascript file loads and the editor renders. Beyond
that I have not verified any functionality.

Major changes:

* Removed the default language of ['en'] from Tinymce::Hammer.languages.
  You can add non 'en' entries and they should still load.

* Changed the default theme from 'advanced' to 'modern'. The advanced
  theme is no longer available as of tinymce 4.

* Removed some of the default init values that were specific to the
  'advanced' theme.

* Removed the ability to toggle source vs minified. The option still
  exists, but this release of tinymce did not ship with non-minified
  source.

* Updated the paths to plugin and theme js files to combine correctly.