Springboard-like page scrolling

[hpique]

Added Springboard-like page scrolling for when the collection view has paging enabled and updated the example. We needed this for collection views that can only scroll to the page offset, and also it feels more "natural".

This feature required an architectural change: currentView is now a sibling of the collection view instead of its child. This avoids overcomplicated calculations to move currentView with the page change animation. Also, this should work better when the collection view is smaller than its parent.

All the page calculations were added to a separate UICollectionViewFlowLayout category, as they are independent of LXReorderableCollectionViewFlowLayout's logic.

Totally understand if you don't want this change in master.

[lxcid]

Wow thanks for this pull request. It looks cool! I should start spending some time building more examples to show case. I'll try review this and merge this in soon though.

I had this experimental drag and drop branch I used in a project. Although I haven't figure out how to merge it into the master, maybe with this I can try to replicate some bit of spring board's behavior! Should be cool. Although one of the reason I couldn't merge in the branch is that it is causing more problems to an already problematic animation when shifting cells.

[hpique]

Let me know if there's anything I can do to help.

Yes, more examples would be nice to simplify testing. And maybe a unit test project.

[mRs-]

Hey, do you find some time to merge this?

[roiholtzman]

Hey, This is a great addition! I would really like to use this flow. Can you please share a project in which it's implemented? Or maybe explain how to use it? Thanks, Roi

[hpique]

@roiholtzman I'm not actively supporting this fork. Feel free to take over!

[roiholtzman]

Does the latest version suppose to handle scrolling that looks like the iOS springboard?

[hpique]

That works like, not looks like.