I guess we don't have indent here?
Bring back the cache_static module

We had a cache_static module but I turned it off because it was
misbehaving: https://botbot.me/freenode/gittip/msg/4196280/. I'm
bringing these hooks back because it looks like we need to configure
cache headers to make it work with MaxCDN. There are facilities in the
MaxCDN dashboad for working around various issues, but they don't appear
to be working for me, and I'm getting less than stellar response from
the on-page live chat over there. So this is me trying to change the
headers at the origin so we start seeing cache hits at MaxCDN. I've set
up a pull zone for QA at MaxCDN so we can fully test this front to back
before deploying to production.
Let's add the indent function to post_compile
Fix bug where non-versioned assets were 404
Update some docstrings for cache_static
Constrain caching to /assets/ instead of /assets

What if someone has a username assets-oh-yeah-assets?
Standardize logic for inbound cache hook
Only cache things under %version
Fix regressions in request API usage for caching