[DOC Beta] Remove duplicate actions documentation.
[BUGFIX beta] Fix `Ember.isArray` on IE8

The previous code couldn't check correctly.

``` javascript
Ember.isArray([]);
//=> false
```
[BUGFIX beta] Fix ember-runtime suites in IE8.
[BUGFIX beta] with-controller cleanup.

Removes unneeded `Ember.get` calls when direct property access would
work properly.