diff_drive: odometry refactoring
diff_drive: fix unit test (bullet types)
diff_drive: fixed linking to urdf
fix heading normalization, using ROS angles lib + sort members constructors
Merge pull request #1 from efernandez/diff-drive-stuff

fix heading normalization, using ROS angles lib + sort members constructors
Merge pull request #4 from po1/diff-drive-stuff

Fixes and refactoring in diff_drive_controller