Add 'overflow: hidden;' to blockquote styles to prevent overlapping

The absolutely-positioned quotes tend to appear in weird places when
the quote is shown beside an image: http://i.imgur.com/LpZDJbk.png

The overflow: hidden; rule forces the block to be separately
positioned because it establishes a new block formatting context
http://i.imgur.com/sAJmrvK.png
http://colinaarts.com/articles/the-magic-of-overflow-hidden/

Change-Id: I0acec6e724e9872c679d03007545c0efd1437235
Merge "Add 'overflow: hidden;' to blockquote styles to prevent overlapping"