Adding support for camera rotation as a command-line flag

[mtlynch]

I just repositioned my camera and the only way to do it was upside down, so I realized this is probably a useful feature.

[coveralls]

Coverage decreased (-0.8%) to 80.066% when pulling 81ef42d895479df003c1a47749695e84fdc3e658 on mtlynch:flippy-floppy into e6e484e65cbf8521e9f0d57ec588d67e6356f2a1 on JeetShetty:master.