Mesh.faces is deprecated, this fixes an exception thrown in blender API 2.68 with "Use colors"

More information here
http://www.blender.org/documentation/blender_python_api_2_63_7/info_gotc
ha.html#ngons-and-tessellation-faces
Merge pull request #1 from scottvdp/fix_mesh_faces

Mesh.faces is deprecated, this fixes an exception thrown in blender API ...