BUG: layout for non-python <pre>
Merge remote-tracking branch 'origin/master'
Adapt example to newer scikit-learn API
First sketch of hide/show for paragraphs.

The goal is to have a shorter display for presentations.
CSS: Clear floats after 'hr'
Misc formatting
ENH: add the folding in the Matplotlib tutorial
Fix CSS bug
Prettify collapsing button (and add missing file)
Fix broken image link
Add notes on collapsable paragraphs in the contributors guide