RaP: Remove the ffmpeg version check, hardcode arguments for 0.11+

For BigBlueButton 0.81, we just require that you install ffmpeg 0.11.x
for recordings to function correctly. I'll also add a check to bbb-conf
to verify that the correct ffmpeg is available.
Add an ffmpeg version check to bbb-conf --check
Merge pull request #217 from kepstin/ffmpeg-version-check

FFmpeg version check changes