Remove dogpile caching

First there were bugs with caching objects over 1MB, now
there are bugs with the in memory cache that never expires
objects and boxes running out of memory.

Given that Giraffe should be put behind a CDN like Cloudfront
or Akamai (or roll your own with Varnish) you should already
have a super cache at the HTTP level and caching internal objects
and stuff is likely not necessary.
Merge pull request #26 from steder/disable-dogpile

Remove dogpile caching