First pass at "pks generate_cache"

[alexevanczuk]

• get md5 of filename to pass
• add test for cache file
• set cody directive
• write failing file cache test
• fix compiler errors
• move test to be a unti test, get it to almost pass
• start working on use serde...
• set max width to 80 for my small personal laptop
• start updating test...
• delete dead code
• implement proper shape serialization
• getting closer
• add to gitignore
• delete tmp
• getting closer
• getting a lot closer...!
• get tests to pass