UILabel instantiation called on each layoutTrack

[mattgallivan]

I was having an issue with labels being recreated on view resize. Specifically, the labels appeared to drop in from the top left which wasn't exactly what I wanted. This was a result of the labels being recreated whenever layoutTrack was called.

To fix this, I made a change so that the labels are only recreated when the names array is set. layoutTrack then only modifies the frames of the labels. When animating, this looks a bit better (in my opinion).

Is this a modification you'd look at a pull request for? (I'm not sure the extent of my changes but I believe they function correctly.)