Re #221 @ namepicker bug

Just committing it to a branch to make it easier for somebody else to
look at it. Left a bunch of debug stuff in there. The action is in
namepicker.js, reddit.js (edit_usertext(), reply()) and the usertext
template.
updating to the latest at.js
use the vendor'ed version of at.js
fix so that at.js works on multiple comment forms on the page
Merge branch 'reply_atnamepicker_bug'