v1.5.7

A few minor changes:

• Added --re-encode-audio boolean option, see #31
• Added --threads <int>, --threads-input <int> and --threads-encoding <int> options to pass through to ffmpeg's -threads arguments (see #30); --threads-input and --threads-encoding take priority, but --threads will be used for either one of the others that isn't specified
• minor tweak to swears.txt