Orientation, position, and block callback support

* Added support for landscape and autorotation.
* Added support for positioning the view at the top or bottom of the
screen.
* Added optional callback blocks that are invoked after the view is
shown, and after the view is hidden.
Top position on iPad

Displaying the notifier in the top position on iPad seems to cause the
view to appear too low, using 0 as the status bar height fixes this,
not sure why :s
Merge pull request #1 from palringosteve/master

Added orientation, position, and callback block support