Add header to minified JS files.

[boughtonp]

There's nothing in the zxcvbn.js file to identify what the project, license or version is.

It would be useful to have a simple header included, such as:

/*
    zxcvbn - realistic password strength estimation
    Updated: 20130203032247
    Project: https://github.com/lowe/zxcvbn
    License: MIT
*/

[tracker1]

@lowe Could probably just create a quick js file that will output the header, then whatever input it's getting, then you could just pipe the browserify output to this script, then through to the destination...