Fix browser usage by removing BOMs

Thanks for this project!

Your files begin with a Unicode BOM, which Node has no trouble with. However, when browserify mashes all the files together for `client-side.js`, the BOMs end up in the middle of the file, and my browsers choke.

Apparently this has been noticed, but not yet fixed, by browserify folks: https://github.com/substack/node-browserify/issues/313

I removed the BOMs, and also cleaned up things around `Changeset.prototype.apply`. I hope this is useful.