BUG: Shnaton parser is insensitive to changes if a course is already in cache

[matanel-oren]

There is no mechanism that checks if an html file of a course was changed after we toke and store it.
I didn't see where we re-download the files that already in cache. It is not necessarily in touch to the parser, probably should be done in a separate script.

[asaf-kali]

You a correct, that is a good point. The cache was originally made for quick development purposes, and not for production. This needs to be addresses.