Use vendored template compiler.

Recent changes to Ember 1.2.0-beta.3 broke compatiblity with templates 
compiled with prior versions of the `ember-template-compiler`.

This change allows us to use the version bundled in Bower with ember itself.

Additional Notes:

* `grunt-ember-templates` added support for using custom
 templateCompilerPath/handlebarsPath in v0.4.17 (see
[here](https://github.com/dgeb/grunt-ember-templates/pull/53)).
* The Ember package in bower is now publishing the template compiler
 (see

[here](https://github.com/components/ember/commit/a1fc1f0f77d6cbeb854c9ba5ad328977e3e08d90)).
* A PR has been submitted to Ember (see
 [here](https://github.com/emberjs/ember.js/pull/3776)) to publish the
 template compiler along with release/beta/canary builds.