Fix UI jerkiness when calling selectTabAtIndex

You can see the underlying bug in the sample app prior to this patch. 

Run the sample app and turn on slow animations (cmd + t in the simulator). Tap the 'Tab #5' button and notice that the tab bar immediately changes to tab 5, then animates left, then jumps back to center on tab 5.  

In the debugger you can see that this is because it's hitting [self.tabsView scrollRectToVisible:frame animated:NO] in scrollViewDidScroll:
Fix layout subview when a tab bar controller is used
Set scrollsToTop to NO for tabsView for other scrollviews to handle
Merge pull request #31 from l4u/patch-2

Set scrollsToTop to NO for tabsView
Merge pull request #27 from igmcdowell/master

Fix UI jerkiness when calling selectTabAtIndex
Merge pull request #30 from l4u/patch-1

Fix layout subview when a tab bar controller is used
Fix for crash if the number of tabs is zero.
Another fix for crash if number of tabs is zero.
An example implementation of reloading content after a period of time. We can say this is a simulation of remote content fetching.
Set the color of temporary view controller’s view’s background to clearColor, so that there won’t be a UI jerkiness when user tries to scroll the content while it’s loading.
Added DS_Store to gitignore.
Lowered required iOS SDK version to 6.0

It was set to 6.1 but I don't think there's anything that requires
strictly SDK 6.1.
Fixed a tab scrolling bug.

Before this, sometimes tab won't follow by scrolling when content view
is paged by swipe gestures. This was caused when `animatingToTab`
property is set to `YES` and never gets back to `NO` again. So I just
worked around this by adding a completion handler to cases that was not
handling this property. I'm not sure that was intentional or not, but
for me this fix works well.
Lowered target iOS version of xcodeproj as well.
Fixed #35.

The first plan for this fix was just to workaround not to pass
`NSNotFound` to `selectTabAtIndex:`, but I found `selectTabAtIndex:`
doesn't take out-of-bounds arguments into account. In private methods
like `viewControllerAtIndex:` handles invalid arguments collectly so I
decided follow this way. Notice that `selectTabAtIndex:` is a public
method which behaviour will be changed by this fix.
Merge pull request #38 from akisute/fix/35

Fixed Issue #35.
Merge pull request #39 from akisute/fix/animating

Fixed a tab scrolling bug.
Merge pull request #40 from akisute/fix/podspec

Lowred target iOS version (project/podspec) from 6.1 to 6.0.
Merge pull request #41 from akisute/fix/gitignore

Added DS_Store to gitignore.
Fix issue

Fix if double tap same tab in short time (when animate not done),
change page view animate will too faster issue.