Changed the way subprocess args are called, it was causing issues on windows and ubuntu.

Also changed the settings file:
## -- Video settings
FFMPEG = os.path.join(EXTERNALS_ROOT, 'ffmpeg', 'bin', 'ffmpeg.exe')

H264_BITRATE = 5000
SCRUB_DURATION = 60

FFMPEG_ARGS = [
    '-vcodec', 'libx264',
    '-b:v', ('%sk' % H264_BITRATE),
    '-pix_fmt', 'yuv420p',
    '-acodec', 'libvo_aacenc',
    '-b:a', '56k',
    '-ac', '2',
    '-y'
]
FFMPEG_SCRUB_ARGS = ['-x264opts', 'keyint=1:min-keyint=8']

## -- Image settings
IMAGE_SIZE_CAP = 5120
IMAGE_SMALL_SIZE = 600
THUMB_SIZE = 256