Remove BOMs

Browsers dislike \ufeff showing up in the middle of a script, which
happens when we bundle with browserify.  So we remove all BOMs in this
project.

Related: https://github.com/substack/node-browserify/issues/313
fix comment, adjust parameter name

`Changeset.prototype.apply` had a comment incorrectly copied from
`Operation.invert`.  Fix this, and also change the parameter name to
`text` to match the operation `apply` methods.