Absolute URLs for links appearing in feed

note that this changes the oft-used byline()
Relocate tag wrangling CSS
Move statistics styles out of sandbox
Move form modes out of sandbox
Issue 3418: Multiple collections doesnt catch moderated status
Issue 3383: Challenges: Empty white box on sign-up form
Merge branch 'master' of git://github.com/otwcode/otwarchive into isue_3383
Issue 1859: Challenge settings don't catch contradictory dates
Issue 1859: Challenge settings don't catch contradictory dates
Issue 2619: Add prompt to Unposted claim blurbs
Adding changes to subscriptions_controller and subscriptions index.html.erb
Counting unique unwrangled tag uses

There are a lot of whitespace changes too, because I'm a bit compulsive about spacing standards, but the main actual change is a bunch of .uniq for the unwrangled by_type counts.
Issue 2249: Clarifying errors on Prompt Memes
Adding tests to check prompt meme error notice
Issue 2215: Error 500 on GE Summary page
Issue 2215: Adding tests
issue 3459: Humanize model names in errors
Issue 3459: Adding test
added new specs
invite requests and user acceptance of invite