MSIE 10 and 11 support, plus build minification

These changes get us a step closer to cryptocat on Internet Explorer. I'm personally not interested in writing a BHO for IE use in Windows (Just install Chrome!), but in order to facilitate writing a Windows Phone 7/8 app, I would like to see these changes made to cryptocat. The build changes to minify javascript are optional, but I thought it would be wise to minimize our memory footprint on mobile devices.

From everything I've read about the PRNG in lib/uheprng.js, this thing may be more secure than the built-in PRNG's for modern web browsers. It's at least a high quality PRNG that should not introduce vulnerability to the product via poor random values. It is only necessary to support MSIE 10, which I need for Windows Phone 8 support as an app.