Allow installing CWStatusBarNotification in projects using iOS 6. It’s up to the user to NOT CALL this library under iOS 6.
Allow callers to specify a block to be run on completion of dismissal animation.

This allows a workaround for the issue where after dismissal, the status bar returns to having
black content, regardless of whether white content should be shown instead. The caller can now
call setNeedsStatusBarAppearanceUpdate in the completion handler to ensure that the system
always draws the correct colours in the status bar.
Allow iOS 7 status bar notification to be modified even while visible
Fix a bug where status bar notification could only be used once.

This change re-uses self.statusBarView as well as self.notificationLabel, but creates a new UIWindow
for each notification. The crucial part, though, is to reset the label’s transform to CGAffineTransformIdentity.
If you were using CWNotificationAnimationStyleBottom, the dismissal animation scaled the height of the label
down to zero without resetting it, which meant that while it was technically being reused properly, it wouldn’t
display any pixels since it had zero height.
Merge pull request #1 from sadlerjw/compatibility-changes

Compatibility changes