Grunt Clean to remove node_modules

if you run "grunt setup" it'll remove the node_modules sub-folders in addition to the usual preening and concat. Otherwise just run  `grunt clean` to remove the folders.
Useful for people who install things via bower, as it produces
an error when trying to load the Chrome extension.

I was trying to figure out what was up with the line-endings (I'm on Windows right now) but git decided it didn't like me sorry.