Added .inRunLoop to Function prototype extensions

This change adds `inRunLoop` to the Function prototype to relieve you of the duty of wrapping all your callback code in `Ember.run`. 

```javascript
Ember.$.ajax("/url", "GET", {
  success: function(result) {
    obj.set('foo', result);
  }.inRunLoop()
});
```

which is shorthand for 

```javascript
Ember.$.ajax("/url", "GET", {
  success: function(result) {
    Ember.run(function() {
      obj.set('foo', result);
    });
  }
});
```