v0.2.0

Video IO v0.2.0

New:

• all nodes ported to Python
• all nodes ported to BasicNode base class
• all video writers switched to using FFMPEG subprocess with stdin/out
  pipe
• param "codec": set output codec (default: mjpeg)
• param "quality": set output compression quality when using lossy
  codecs (default: 24)
• param "encoder_args": set any additional FFMPEG encoder arguments
• param "publish_every_nth_frame": set publishing rate of video_player

Updates:

• C++ code to subpackage as video_io_cpp