Add preliminary DNS resolution

Surely this could be a lot smarter. In particular it just fails
on several types of errors.
Make the Expires header parse as a plain string

Google is sending these headers with value '-1', which doesn't parse.
Merge pull request #12 from brson/master

Basic DNS and a parser workaround
Merge remote-tracking branch 'chrismorgan/master' into HEAD
Fix clean target
Merge pull request #4 from brson/master

Merge with upstream. Fix make clean