Including gmail.js

I'm trying to include gmail.js from here. But the object gmsrc is invalid, the function get.user_email() fails. I'm trying to develop a Chrome extention, the chrome developer tools (F12) tells me

Uncaught TypeError: Cannot read property 'user_email' of undefined

Here is my code:

var jq = document.createElement('script');
jq.src = "http://ift.tt/17YXcKA";
document.getElementsByTagName('body')[0].appendChild(jq);
var gmsrc = document.createElement('script');
gmsrc.src = "http://ift.tt/1xeQ2wo";
document.getElementsByTagName('body')[0].appendChild(gmsrc);
console.log("Scripts loaded, Start playing ...");
var name = gmsrc.get.user_email();
alert(name);

Where is my mistake?