Add onChange option

This option allows the user to specify a callback that is called
whenever the plugin changes the state of a checkbox.
Fix color animation plugin
Add syntax highlighting
Use new onChange option in demo
Remove color animation

It doesn't seem to be working correctly anyway.
Upgrade jQuery to v1.10.2
Fix the plugin with newer versions of jQuery

Use .on() for events and .prop('checked') instead of .attr('checked').
Requires jQuery v1.7 or greater.  Tested with v1.7.0, v1.8.0, v1.9.0,
and v1.10.2.