Add CSS for making images stay inside container

By uploading an attachment and prepending a bang to the embed code an
Editor can embed images. This CSS keeps them inside of their container
and resizes it down when smaller than desktop.
Merge pull request #59 from alphagov/add-css-for-images

Add CSS for making images stay inside container
Don't show title twice when showing manual contents

Remove the redundant heading (it's displayed in the main bar at the top)
and bump the size of the summary text to 24.
Merge pull request #60 from alphagov/dont-duplicate-manual-title

Don't show title twice when showing manual contents