add missing dependency to catkin_package()

[roehling]

Message generation depends on geometry_msgs, thus this dependency must be propagated in catkin_package().

[jack-oquin]

Thanks, Timo! Good catch.

[mikepurvis]

Doesn't this only affect linking? I thought a build_depend/run_depend was sufficient for messages, since they're header-only.

[jack-oquin]

The catkin API how-to recommends it, so it seems better to do it that way.

It does currently seem to work without the explicit find_package() component.