Adds video playback using omxplayer

This release adds hardware accelerated video playback using omxplayer. Omxplayer must be installed system wide for this feature to work. Supported file formats mp4 h264 videos.
This also corrects a missing requirement of pillow in requirements.txt.

First stable release

SliPi was designed to provide a robust solution to running a slideshow info display off of a Raspberry Pi. This project uses the Pi3d library and shaders included in the pi3d demo library. Together with this python 3 project a series of png or jpg images will continuously display. Screen size, fade time and more are configurable by using config.yaml
(Example included as EXAMPLE_config.yaml).