用gazebo模拟的时候出现了下面这个问题
Could not load controller 'joint_state_controller' because controller type 'joint_state_controller/JointStateController' does not exist
原因是这几个包不是自带的，必须要手动装，解决方法在https://github.com/qboticslabs/mastering_ros/issues/7
$ sudo apt-get install ros-indigo-joint-state-controller // This will install joint_state_controller package
$ sudo apt-get install ros-indigo-effort-controllers //This will install Effort controller
$ sudo apt-get install ros-indigo-position-controllers // This will install position controllers
