Temporary fix for brid.gy comment clobber (#510).

This allows posts to appear, but the cost is that they all appear to be from brid-gy.appspot.com in the by line...
Closes #546: Provides a hook to allow a plugin to optionally expand any links in the body text. 

Note: Since this is likely to be called several times, it should be done fairly efficiently. Probably cached.
Passing the object in question, since this provides a way of caching short urls until #371 is merged
Alignment tweak to users
Standardizing spelling
Revised hashtag parser
Less invasive username parsing
Merge pull request #557 from mapkyca/user-pane

Alignment tweak to users
Merge pull request #547 from mapkyca/expanding-short-urls

Adds a hook to expand on short URLs in body text
Merge pull request #538 from mapkyca/fixing-webmention-clobber

Temporary fix for brid.gy comment clobber (#510).
Brid.gy likes, shares and RSVPs get stored explicitly