Firefox add-on index.js with elegant hack to load a page-mod script from the add-on's root folder rather than from under its /data folder (for http://stackoverflow.com/questions/22656494/contentscriptfile-dont-work-in-pagemod)

index.js

var self = require('sdk/self');
var pageMod = require("sdk/page-mod");

pageMod.PageMod({
	include: "*.github.com",
	contentScriptFile:  "resource://<your_extension_name>/somefile.js"
});