`openingDone` event

[pisi]

Comment from Ben Palmer extracted from #27

Would be great to add a callback for when the animation ends. I have tried hooking onto the 'opening' or 'opening_tick' method but neither worked. So a callback like:

$('#reel').reel({
    onEntryEnd: function(){
        /* Do something */
    }
});

[pisi]

OK, I will add a new event openingDone, which will be triggered at the precise moment the opening_tick gets unbound. It won't be a .reel()'s option, but rather a standard event triggered on the instance.

$('#reel').bind('openingDone', function(){
    /* Do something */
});