Lots of updates and changes

This PR includes the changes from #2

What I've done is basically change part of the ChiptunePlayer API to interact more nicely, including adding a few new metadata discovery functions and duration

I also completely redid the CSS for the page, to make it responsive and display more nicely at smaller resolutions. I've also added a few more chiptunes, to display the more intensive playability of it.

If you want to take a look, I've got it online at http://danieloaks.net/chiptune2.js/