Implement Diceware Passphrase Generator

Note: This is a first swing. I do not have the hardware necessary to test it properly at the moment.

Fixes #163 
It's easier than you think. Here's how I would go about it: Instead of loading the wordlist in the Diceware constructor, move that out into a function load(callback)

Diceware.prototype.load = function(callback) {

Then at the end of the function you call from $.get(...), run:

    callback();

In the client code you'd do:

    var dw = new Diceware();
    dw.load(function() {
       ....
    });