Merge pull request #38 from plu/accessibility

Let subclasses access the dismissbutton.
Merge pull request #39 from plu/own-queue

Use own queue to be able to cancel queued noticeViews.
Fixed #40: Height for large error example is broken
Fixed #42: tapToDismissEnabled

Also fixed the potential issue of initializing properties using
self.xxx from the designated initializer method.