control.py self.msg() calls try to join lists with strings

In control.py, at the following instances, str is being concatenated with a list, which raises an exception:

1. line 3129
2. line 3557
3. line 3952
4. line 3972

Example: line 3129: raise stem.ProtocolError('SETEVENTS rejected %s' % ', '.join(failed_events))

raises exception. Can be fixed by using: raise stem.ProtocolError('SETEVENTS rejected %s' % ', '.join(str(v) for v in failed_events))

Trac:
Username: kamin07