Embed Handlebars parser into htmlbars-compiler.

* Embed required Handlebars parser modules into htmlbars-compiler.
* Migrate to broccoli-funnel instead of broccoli-static-compiler.
* Add htmlbars-utils package for safe-string (otherwise handlebars
  modules would be needed for most packages).

This will allow Ember's test suite to not be polluted by Handlebars
version included there.