Removed deprecation warning about using UITextAlignmentCenter keyword
Added a reference to the SVWebViewController object to be passed as an argument to the delegate which is to create the custom uinavigationbarbutton.
made the back and forward buttons be disabled when they can not go back or forward respectively.
Added better support for html5 pages, so that the navigation bar will be updated correctly and the webViewDidFinishLoad delegate is called once a new page has been loaded.