Do not use abbreviated locale versions of month/whatever, because it seems that
this is not standard (e.g. MacOS abbreviating differently than GNU/Linux).
The old get_relative_path() implementation assumed os.sep == '/',
which doesn't hold on MS Windows. The new implementation uses
split_all() for a more general component count.
I added path_to_url(), because the:
'/'.join(split_all(path))
idiom was showing up in a number of cases, and it's easier to
understand what's going on when that reads:
path_to_url(path)
This will fix a number of places where I think paths and URLs were
conflated, and should improve MS Windows support.
