Automagic previews
Automagic previews
Old previews are removed properly
Merge branch 'feature/preview' of github.com:Derkje-J/programming-life into feature/preview

Conflicts:
	app/assets/javascripts/controllers/cell.js.coffee
	app/assets/javascripts/views/popover.module._.js.coffee
	app/assets/javascripts/views/raphael.cell.js.coffee