Add u-url classname to post permalink anchor

…along with `url` classic fallback for consistency with e-content entry-content.

This change allows me to click through to your posts when reading them in my feed reader http://waterpigs.co.uk/intertubes/feed/

It also clears up one of the indiewebify.me h-entry validator suggestions: http://indiewebify.me/validate-h-entry/?url=http%3A%2F%2Fwerd.io%2F2014%2Fcyclists-of-the-bay-area-heed-my-call