track git sha for files of interest

we will use this in a future commit to avoid re-reading files that
haven't changed
tweak readme header
Add force option and speed up hash testing

Pull all of the files for a proejct and their SHAs at one time instead
of querying for each separately.

Add a --force option to cause files to be re-read even if their hash has
not changed.
a few more performance tweaks for loading
add indexes to make deleting faster