Reader: Don't relayout text/media if not visible. Clear queue on dealloc.
Follow up to #149.
Reader: Relayout text even when not visible.
Assumes things will be ready to go when navigating back to the view.

Refs #149
Adding documentation.  Renameds abort method to be more descriptive.
Merge pull request #392 from wordpress-mobile/issues/149

Reader: Don't relayout text/media if not visible. Clear queue on dealloc...