Unrecognised option keys should raise an exception

Hi Scott,

Update: It also appears that array values have also been deprecated. eg this no longer works: :enter => [:send_notification, :update_status]

After upgrading from acts_as_state_machine, I had something like this: aasm_state :despatched, :after => :send_notification

After much head scratching, it appeared that :after had been deprecated in favour of :enter.

I couldn't find this in the rdoc, so I reckon it would be ideal to raise an exception if any options are not recognised.

btw I like the new version - it's much stricter than the old one, raising an exception when attempting an invalid transition.