Fix readme code sample

Fix a typo, and update(?) some of the structure to work again with iron.

The code works right now, but just logging the parsed json is not that useful. An example for getting the values of the parsed json out would be awesome. I tried to figure it out, but got bogged down when trying to bridge what I learned about `serialize::json` back to this library (total rust noob).

(I wrote some similar things at [iron/iron.github.io/ #8](/iron/iron.github.io/pull/8), excuse the redundancy)