Adding mainScene filename to error message in expandLink
Deleting normals on subdiv meshes converted from Houdini.

Subdivision meshes should not have normals, but they tend to get added accidentally when dealing with many meshes in a single SOP, as that would extend the normals attribute to all meshes. We force N to be excluded when converting subdiv (catmullClark) meshes.
Merge pull request #187 from andrewkaufman/deleteNormalsOnSubdiv

Deleting normals on subdiv meshes converted from Houdini.
adding quotes
Merge pull request #186 from andrewkaufman/expandLinkErrorMessage

Adding mainScene filename to error message in expandLink