[BUGFIX beta] Make Ember.Handlebars.makeViewHelper warning useful.

* Adds `ember-handlebars-compiler` to the list of packages that are
 tested.
* Uses `ViewClass.toString()` in the assertion thrown from
 `Ember.Handlebars.makeViewHelper`.

Example message before this change:

``` Assertion failed: You can only pass attributes (such as name=value) not
bare values to a helper for a View
```

And after (using EAK resolver):

``` Assertion failed: You can only pass attributes (such as name=value) not
bare values to a helper for a View found in 'appkit@component:api-file-link:'
```