Publishing Meshes to Rviz

Meshes are published similarly to spheres and arrows.

The only major change is replacing the marker type with MESH_RESOURCE and using 

marker.mesh_resource = "package://pr2_description/meshes/base_v0/base.dae";

after setting the marker.type.

A quaternion of (0,0,1,-1) placed the head in the correct orientation.