Convert daemon threads back into normal threads.

This may need to be reverted if CTRL-C handling breaks, but everything
works fine so far in testing.

Resolves issue #95.

sleekxmpp/xmlstream/scheduler.py

@@ -134,7 +134,6 @@ class Scheduler(object):
         if threaded:
             self.thread = threading.Thread(name='sheduler_process',
                                            target=self._process)
-            self.thread.daemon = True
             self.thread.start()
         else:
             self._process()