videoread module for retrieving frames from video
Improve config handling and docstrings

ffmpeg path now set in user_config.py; example file is updated to reflect
this.
Started stage shift correction and got framegen
Merge commit
fixed vidtools bugs
Finished off video reading tools, started contours

Video reading is slow and RAM-intensive but works. Contours are easy to
find.
Created Worm class

Smooths image data and segments using the length down each side.
Improved get_pointiness