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.

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Changes to Ember build system to match this will be in a follow-up Ember PR.