Some fixes and changes

Hi James,

first of all thank you very much for that plugin, I like it, nice, tiny and unobtrusive, great work!

I just implemented your plugin and found several bugs for the watching feature, basically checking classes that didn't exist, comparing original and new Content that didn't have the same source and smaller stuff.

I also enhanced the plugin to have the used classes set via settings.

no idea if you want to incorperate any of my changes into a future release, but if so, feel free =D