Fix AMD compatibility in Shotgun.js

The AMD compatibility still seems broken ref @ Issue #1. After a RequireJS optmization the app throws the notorious, "Mismatched anonymous define() modules" error in the js console.
I have applied a fix in Shotgun.js and using the below given rquirejs config seems to have fixed the issue;
RequireJS main.js
=================
shim: {
        "shotgun" : { "exports": "Shotgun" }
}