Set hideToolbarOnClose and hideNavBarOnClose once

When a UIActivity presents a UIViewController,
such as UIActivityTypeMail, 
upon return viewWillAppear: will be called again
thus resetting hideToolbarOnClose and hideNavBarOnClose.
Avoid by setting them during viewDidLoad.
Merge pull request #20 from mvasilak/master

Set hideToolbarOnClose and hideNavBarOnClose once