bind-class bug

[karneaud]

apparently if you try to bind-class to an element that HAS more than one class it is overwritten rather than appended and detached.

[dgileadi]

Thanks for reporting this and your previous bug. As you're finding out this library hasn't ever been tested and is therefore buggy. Hopefully I'll get some time to work on it and fix bugs, but for now I'm going to put a big notice in the readme that says it's incomplete and buggy.