New implementation of Tabby

[RamonGilabert]

All right, here it is. The new implementation of Tabby. It features:

• Behaviors (a way to add custom behaviors to the bar).
• A Collection View to easy add stuff into the it.
• Different constants and properties.
• Different set of animations.

With all that, there's one missing thing that you'll see in terms of a TODO. That is, find the difference when you add new items and do whatever is best in the tab bar. That is, delete, insert or reload all the way. Something similar to what we have in Spots.

I believe, though, that we could just put it right away. And then add it later.

It'd also be nice to set up Carthage.

What do you think, @hyperoslo/ios?

[zenangst]

Should we drop the prefix in the naming?

[RamonGilabert]

I don't want to be calling TabbyController -> Controller or TabbyBar -> Bar.

[zenangst]

Good point, screw it. I like this PR... MERGE!

[zenangst]

[RamonGilabert]