delegate rename, animation speed, storyboard friendliness

[rae]

Renamed delegate to splitDelegate to avoid confusion and possible conflicts.

Changed minimum view width to 100. This shouldn't really be hard coded at all though. Added MG_PANESPLITTER_ANIM_DURATION to control the speed of using [UIView animateWithDuration:].

Moved call to [self setup] to viewDidLoad, which makes MGSplitViewController Storyboard-friendly. setSplitPosition now uses [UIView animateWithDuration:] instead of old [UIView beginAnimations .. commitAnimations].

[rae]

Comments from the review on Reviewable.io

---

^{Classes/MGSplitViewController.m, line 876 [r1] (raw file):} This is a good idea

---