Workaround for Issue #88 

This works around the problem described in issue #88 by running monitoring the changes feed with a pooled AsyncTask rather than the default AsyncTask.  

Also as part of this change, I needed to depend on a later version of the com.google.android.android artifact in maven central.  The earliest version I could find which had the AsyncTask.THREAD_POOL_EXECUTOR constant was version 4.0.1.2.

After digging into things a bit, it seems that the deeper fix would be to use a Service for following the changes feed, which would emit events that the eventually cause the UI to get updated via the main thread.  

In the meantime, though, this fixes the immediate problem and effectively goes back to the original behavior of AsyncTasks at the time this code was written.