Fixed model specs, some of which I broke.

There's a fight here between DatabaseCleaner strategies - simpler to use
the default :transaction for model specs, but Capybara lives in a
different world where different connections are in play and
:transactions don't work. So, while introducing the more cumbersome
(though with more control) DatabaseCleaner gem and its truncation
strategy, I forgot to make sure the model specs had the fixtures present
that they depend on. This is fixed up now.

The user spec for invalid email was also failing - the regex there is
not savvy enough to handle rejecting two @ signs, so I made the invalid
value something still invalid to get it passing -- real regex validation
of email is ... impossible, so we'll roll with this and move on.