layout: `flex="flex"` should be replaced to just `flex`

[e-oz]

Please compare:
http://codepen.io/evgeniyoz/pen/ojZoJb?editors=100
http://codepen.io/evgeniyoz/pen/qOrVgO?editors=100
Was not an issue in 0.11.0, but issue in 0.11.2 (easy to fix, but still should be noted in changelog, to save time).

[mattiLeBlanc]

probably related: Flex turns into class="flex-flex"

#5044