Fix a crash when TDSocketChangeTracker gets an error

During the -errorOccurred: method's call to [self stop], the delegate would end up releasing the tracker,
causing it to be dealloced prematurely. Moved the stop call to the end, and for safety's sake added a
temporary retain during the entire stream:handleEvent: call.
(Bug reported by Joerg Birkhold.)
Bump version to 1.004