Updated social icons

(Formerly pull 689. I squashed the commits at Alexis' request and couldn't update that pull request.)

New icons: aboutme, bitbucket, google-groups, hackernews, reddit,
slideshare, speakerdeck, vimeo, youtube

Also, fix spacing below a line-block.

Try this in ReST::

	| First line
	| Second line
	| Third line

	New paragraph.

	Another paragraph.

Notice how the line-block runs into the first paragraph without the new CSS.