Fix bug occurs when tapping tabItem and swiping viewController at the same time

[hiragram]

• Tap tabItem
• Swipe or tap viewController immediately (before tabItem's animation has finished)
• tabItem shows that Blue viewController is selected, but Red viewController is actually selected. (And after that, Yellow viewController disappears and be skipped)

Sometimes app crashes but not every time.

2017-06-02 14:05:39.322094 TabPageViewControllerDemo[5856:1863363] *** Assertion failure in -[TabPageViewController.TabPageViewController queuingScrollView:didEndManualScroll:toRevealView:direction:animated:didFinish:didComplete:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3600.6.22/UIPageViewController.m:2083
2017-06-02 14:05:39.324377 TabPageViewControllerDemo[5856:1863363] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'No view controller managing visible view <UIView: 0x115f10400; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x17403f060>>'
*** First throw call stack:
(0x191e151b8 0x19084c55c 0x191e1508c 0x1928cd02c 0x1984d8ae0 0x1985aacbc 0x1985aaa14 0x1985a6b38 0x1985a97b8 0x1985acac4 0x1985accec 0x1985a7aa8 0x197fde050 0x197e73370 0x197e72eac 0x19506af24 0x19506add0 0x192082094 0x191daae50 0x191dc3218 0x191dc29cc 0x191dc04b0 0x191cee2b8 0x1937a2198 0x197d357fc 0x197d30534 0x10004b624 0x190cd15b8)
libc++abi.dylib: terminating with uncaught exception of type NSException

To prevent this bug, I set tabPagerController.view.isUserInteractionEnabled to false in displayControllerWithIndex, then set to true when animation has been completed.
This change works fine with my project currently.

[hiragram]

I made a mistake so I will recreate PR from different branch.

[hiragram]

see #69