"Bad value context for arguments value" deoptimization in `String.fmt`.

This deoptimization occurs when you try to re-assign arguments passed
into the function.

Also, this change swaps slow `Array.prototype.slice` with `for loop`.

before:
![fmt-before](https://cloud.githubusercontent.com/assets/1131196/3981272/36463740-286c-11e4-8bbc-8d3dd80448e0.png)

after:
![fmt-after](https://cloud.githubusercontent.com/assets/1131196/3981279/410d61bc-286c-11e4-92d1-52bdb2d98f74.png)
Update action.js

Re-export ActionHelper.registeredActions for backwards compatibility.
Update computed_macros.js

This sounds more natural
Update morph and use new DOM Helper APIs
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