The first two lines of code:

var React = require('react'),
  classSet = React.addons.classSet;

should be:

var React = require('react/addons'),
  classSet = React.addons.classSet;

The browserify bundle was throwing an error, but I fixed it by requiring "react/addons" in my main file, which adds the "addon" property to React. This should be fixed or the docs need to specify that react/addons is needed.