gazebo_plugins: terminate the service thread properly on destruction of a PubMutliQueue object without shuting down ros
Merge branch 'hydro-devel' of https://github.com/osrf/gazebo_ros_pkgs into terminate_service_thread_fix

Conflicts:
	gazebo_plugins/include/gazebo_plugins/PubQueue.h
Merge pull request #33 from meyerj/terminate_service_thread_fix

another fix for terminating the service_thread_ in PubQueue.h