Moved definitions to 'restify' namespace, added inheritance of Server, Request and Response

1. Moved definitions from global ( evil :) ) context to 'restify' module/namespace.
2. Added inheritance of Server, Request and Response from nodejs 'http' module.
3. Removed 'on' method from Server definition, now is inherited from http.Server
4. Added 'body' property to Request interface

documentation here: http://mcavage.me/node-restify/