Redirect to root for invalid tutor_id in Appointment#new.

Rails `redirect_to :back` does not fail gracefully.  Will need to
implement an alternative.  For now, redirect to root.
Swap backing SQLite3 database for PostgreSQL.

Should make deployment to Heroku much less painful.  Should also
prevent any more database locking during unit tests.  This will
(hopefully) let us switch to the headless webkit driver for
integration testing.
Activate Webkit driver for Capybara.

Shows no signs of database locking -- upgrading to Postgres seems to
have fixed the problem.
Fix broken integration test.

When schedule blocks switched from JS onclick to actual links, the
data attribute tested against went away.  Changed test to look for the
proper link.

Note:  When matching links in Capybara, the link text is required.  For
a `&nbsp;`, use `\u00A0` to match.
Fix race condition in User pages spec.

Switching to Webkit exposed a race condition in testing the
registration form submission.  Instead of expecting a change in the
database, test that the user receives the success flash message.