driver: add dependency on catkin exported targets
driver: fixes a compile error on OS X

I'm not sure why this works on Linux? data is not
a static member of VelodynePacket, it should not
be accessed with an instance.
pointcloud: [style] trailing whitespace
pointcloud: [style] exceptions should be passed by reference
pointlcoud: fixes to reflect changes in pcl-1.7

pcl_conversions is explicitly not a run_depend nor
a transitive dependency as it is only used in the
cc files.
Merge pull request #8 from wjwwood/pcl-1.7_fixup

Fixes for building on OS X and against pcl-1.7