Hacked it into working in Node.js server-side.

Added package.json, node-pagedown-extra.js, and a small blurb in README.md.

Usage:
var pagedown = require("pagedown");
var converter = new pagedown.Converter();
var pagedownExtra = require("pagedown-extra");
pagedownExtra.init(converter);
Fixed bug related to misuse and abuse of globals.
Merge branch 'master' of github.com:jkunkee/pagedown-extra into jkunkee-master
Set up Karma and use it in Travis
Removed unused ruby files