Logger does not display state information

[asobrien]

When using the logging functionality with transitions, the state information of the state machine is not displayed on_enter and on_exit. For example, on entering a state stdout displays:

2015-09-01 13:13:41,528 - transitions.core: Exited state %s

This issue is probably due to an incorrect string formatting in calls to the logger, see below:

logger.info("Entered state %s", self.name)

# should be changed to:
logger.info("Entered state %s" % self.name)