Do not call releaseResources when there's nothing to release
Remove unused member
Better resource management in ComposedCursorLoader

Old code was releasing the old Cursor before new result was delivered.
This might cause issues in very rare case: lazily transformed Cursor
wrapped by a function returning the same object every time.
Register ContentObserver after the first data was delivered

If you register ContentObserver in the background thread before the data
is delivered, and the notifyChange on subscription Uri is called, the
data will be dropped and Loader will try to load the data again. It's a
good idea for further loads, because you do not want to show stale data,
but during first load it's desireable to show any data as soon as
possible.
Do not reload the data when loader is abandoned

When restartLoader is called, the new Loader instance is created in
onCreateLoader callback and the old instance is moved to abandoned
state. In this state Loader should keep the data until the newly created
Loader delivers the results, but it should not reload the data itself,
because the results would be dropped in onCancelled callback anyways.
Expose DisableableContentObserver utility class
Merge pull request #49 from futuresimple/loader-fixes

Loader fixes