Pull htmlbars in via bower.

This allows much simpler updating to new versions, just update the sha
in `bower.json`, run `bower update htmlbars` and boom: new morph
version.
Merge pull request #5321 from rwjblue/pull-in-morph-via-bower

Pull htmlbars in via bower.
Create an ember-htmlbars package and bring in all the deps
streamFor hook / basic Ember.View integration
Template context should be the view itself
LazyValue binding support
Port `loc` helper
Port `debugger` helper
Port `log` helper
Port `view` helper
Port `each` helper
Port `input` and `textarea` controls
Port `bind-attr` helper
Finish porting `bind-attr` helper

(minus tests relying on the `with` helper)
Port `action` helper
Finish porting `action` helper

(minus tests relying on the `with` helper)
Port `if` and `unless` helpers
Port `with` helper
WIP clean up hacks on top of metal-views
Fix some action helper tests