Merge pull request #1 from gareth-cross/master

Corrected covariance issue, topic names, velocity convention and misc other.
Merge pull request #2 from gareth-cross/master

Change to node
Update ublox_gps.launch
Update ublox_gps.launch
add an option to specify node nanme
fix frame_id default
Changed meas_rate to rate
Merge branch 'master' of github.com:KumarRobotics/ublox
Changed launch file to match readme
Set better default for dr_limit in launch file