/odom reports non-zero y velocity

[cburbridge]

'/odom' reports a very small non-zero y velocity when driving normally. When sliding along an object it reports higher velocities. It should always report zero since this is how the real-world scitos behaves.

This interferes with the DWA planner, and may be related to #66.

[kunzel]

PR #101 fixes this issue by republishing the odometry message from morse.

The issue of the drifting robot should also be fixed. There were still little cracks in the floor.