Subscriber tick tock test broken

[stonier]

06:59:37 [ROSTEST]-----------------------------------------------------------------------
06:59:37 
06:59:37 [py_trees_ros.rosunit-test_subscriber_check/test_tick_tock][ERROR]--------------
06:59:37 unorderable types: Status() < int()
06:59:37   File "/usr/lib/python2.7/unittest/case.py", line 329, in run
06:59:37     testMethod()
06:59:37   File "/tmp/catkin_workspace/src/py_trees_ros/tests/rostests/subscriber_check/test_subscriber_check.py", line 101, in test_tick_tock
06:59:37     self.runner.tick_tock(number_of_iterations=50)
06:59:37   File "/tmp/catkin_workspace/src/py_trees_ros/tests/rostests/subscriber_check/test_subscriber_check.py", line 72, in tick_tock
06:59:37     while not rospy.is_shutdown() and self.root.status < number_of_iterations:
06:59:37   File "/usr/lib/python2.7/dist-packages/enum/__init__.py", line 719, in __lt__
06:59:37     raise TypeError("unorderable types: %s() < %s()" % (self.__class__.__name__, other.__class__.__name__))

[naveedhd]

PR #23