fixes library resolving issues on debian based distros
removing avformat_free_context
Use avg_frame_rate instead of r_frame_rate

r_frame_rate is "the least common multiple of all framerates in the
stream". It is deprecated and removed in Libav. Using avg_frame_rate
instead, which is the average framerate of the stream.
adding option to list detected opencl devices
adding configuration functionality
help formatting
increasing pyr-scale and winsize defaults to optimize for quality
make main script handle exceptions
fix minor argparse help typos
adding show preview while encoding option
fix import py_motion resolving issue in __init__
set ocl kernel binaries cache path to user home when testing
fixing some help typos
disable prep and mux with subs if using avconv
remove ubuntu from readme
adding debian install and quality section to README
added verbosity options and formatted some output
only check for ffmpeg/avconv when main is called
add pocl-opencl-icd to README and clarify debian version