AUI-1669

Hey @mjbradford89,

Attached is an update for http://issues.liferay.com/browse/AUI-1669.

@mairatma has left some comments regarding this update at https://github.com/eduardolundgren/alloy-ui/pull/799.

There are a few things to look at:
- Look up the attribute when calling it rather than caching the value to a variable.
- Move ```this._sources.length``` checks closer to where the logic for the code is being used to make the code cleaner and easier to read/understand.

Can you take a look at these and send an updated pull request?

Please let me know if you have any questions.  Thanks!