Adding a test for `transferables` objects

Detecting the `transferables` feature for web workers using [this](http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fast) method.

I used the `blobworker` test as a base since loading an external file might be painful. I cannot think of cases where it would be possible to dispose of `transferables` and not of `blobworkers`.