ever-present tag cloud via context processor

I am very excited about context processors!
:rainbow: sidebar miniprofile, and a major insight about color

In a moment of inspiration, I think that the entire site should be
shades of gray with the enormous, glaring exception of the reds and
blues of voted-upon text, tags (similarly computed from votes), karma
bubbles (likewise), and upvote/downvote buttons; it'll make the site's
flagship feature _really_ stand out.