Navigating through the dropdown should trigger events

[jamesarosen]

For example,

{
  name: 'navigation-up.flapjack',
  flapjack: aFlapjackInstance,
  from: aFlapjackGroupOrLeafInstance
  to: anotherFlapjackGroupOrLeafInstance
  originatingEvent: aKeypressEvent
}

Other navigation events:

• navigation-down.flapjack - down to the next item in the list
• navigation-in.flapjack - open a group
• navigation-out.flapjack - go back to the current group's parent