PMFT face_orientations don't error check properly

[Vyas Ramasubramani]

There are two cases that the PMFT object does not correctly check for the face_orientations object at the moment:

• If an (N_p, N_f, 4) array is passed, there is no check that N_p is actually the number of particles.
• If an (N_f, 4) array is passed, this causes some failure (it may be a seg fault). We should identify why this causes a catastrophic error, and freud should also just fail transparently if there turns out to be a reason we can't do this.

[Eric Harper]

PR #100