Create new index design

Update the index.php file with a new interface/design. Refactor CSS into
new path.

The new interface with which index.php was re-designed looks somewhat like the following:

![bitcoinotc](https://cloud.githubusercontent.com/assets/3946887/5562721/5c900360-8e81-11e4-8d46-bc73864c9819.png)

Thanks for maintaining `#bitcoin-otc`!