IOWA originally used a slightly modified version of the parser found in Mongrel
version 0.3.13.3.

At that time, there was a trie based classifier that was bundled into the parser.
The IOWA version removed that into a separate extension, and also made some other
small modifications to the parser to separate the headers from the params. Now,
8 years later, this seems like a poor idea.

This version still contains some very minor modifications for IOWA, but it retains
the base design where HTTP headers and request params all are inserted into the
same hash.
