Avoid the need of subclassing PullUpController

[penaeric]

I think it'd be better to use composition over inheritance for obvious reasons. In my case, working with a big project, it's hard to change your view controllers to inherit from a new type.
Since the code is abstracted in a nice way, it should be easily doable by moving all the logic to some type of manager. In fact, I've been playing with the code and I have it (mostly) working... I just ran into a couple of what seem small bugs.
I can open a PR once I clean up the code a bit, but wanted to get your take @MarioIannotta to see what you thought about this possible refactor.

[MarioIannotta]

Hi Eric, I totally agree with you.
I'm just a little bit afraid of this "manager thing", I hope singletons are not involved in your refactor :)

[penaeric]

No singletons at all :)
Hope to have a PR soon

[ebsamson3]

To me it makes it most sense to turn it into a container view that you can add a content view controller to.