Content Negotiation (#63)
Bump Sammy.js to 0.7.4

0.7.2 is no longer available for build.
cleaned up extra blanks at eol
sammy was upgraded, correct test
socket.io.min.js is only available for pre-1.0
Added X-Powered-By: Zappa header (#68)
Tests for `X-Powered-By` (#68) and `format` (#63)
Added example to show `format` with explicit mime-type. (#63)
Documentation for x-powered-by (#68)
README: do not recommend using 0.3.
Dependencies: update to ExpressJS 3.1.0
Release v0.4.16