Changeset 76ebb1b in OpenWorkouts-current for ow/migrations

(#29) Add user verification by email on signup.

From now on, when a new user signs up, we set the account into an "unverified"
state. In order to complete the signup procedure, the user has to click on a
link we send by email to the email address provided on signup.

IMPORTANT: A new dependency has been added, pyramid_mailer, so remember to
install it in any existing openworkouts environment (this is done automatically
if you use the ./bin/start script):

pip install pyramid_mailer