Add #anyHands() convenience method to Frame

Instead of

    frame.hands.length > 0

Users can now use:

    frame.anyHands()

Since most Leap-related Cylon activities will involve using hands to control
other bits of hardware, hopefully this can make people's lives a little bit
easier.

Also includes a couple quick tests to go along with it.
Merge pull request #5 from hybridgroup/frame-anyhands

Add #anyHands() convenience method to Frame