ros_diff_drive enhanced with trip counter and command feedback
diffdive enhancements, GetModelState.srv with header inforamtion anhanced removed
Debug message in publishAgentState removed
ros-diff-drive now controls linear and angular speed

As most robots use linear/angular velocity controlers, the ros-diff-drive and required xacro have been modified to simulate this type of control. Acceleration bounds modified for p3dx to real-robot measured values
Merge pull request #2 from todorangrg/indigo-devel_diffdrive_enhanced

ros-diff-drive now controls linear and angular speed
with header on GetModelState srv
Merge branch 'indigo-devel' of github.com:/maxbader/gazebo_ros_pkgs into indigo-devel
Merge branch 'indigo-devel_diffdrive_enhanced' of github.com:/maxbader/gazebo_ros_pkgs into indigo-devel