Add gittip to the list of possible profiles

http://gittip.com -- donation site, pretty self-explanitory.  We could
probably make the donation bit tie in elsewhere, but I'm going to leave that
for a future pull request :)
Merge pull request #808 from RsrchBoy/topic/gittip

Add gittip to the list of possible profiles
Adds icon for gittip.
Identify authors who have clicked ++ in the recent ++ feed.
compare author as well, refs #796
Merge branch 'master' into mo/bootstrap