Added some simple functions to solve the problem from Stefan Eibl of counting...

Added some simple functions to solve the problem from Stefan Eibl of counting faces. Releasing version 0.2.3. Changed facets_loop to voropp_loop.

git-svn-id: https://code.lbl.gov/svn/voro/trunk@119 6221c96e-593b-4ce1-a500-64c4038a1943