Lazy initialization of view controllers and a few more new features.

Added option for setting custom navbar image (AMOptionsNavBarImage).
Added option for hiding separator in cell which is before section header (AMOptionsShowCellSeparatorLowerBeforeHeader).
Added posting notifications when menu show and hide.
Added method for getting view controller by tag.
Added methods for disabling/enabling pan gesture.
Now if the user chooses the same menu item then controller does not changing (menu just hided).
Navbar is made is translucent by default.