Implements email confirmation

Support for confirming initial email address, as well as changing a
confirmed email address (confirmed email address will remain on record
until provisional address is confirmed).

Adds emailConfirmed field to User model, and corresponding database
migration.

Small changes to the email module.

Updates requirements.txt and config.sample.py.
Small email confirmation bug fix

If user had an unconfirmed email in the database, a further edit would
not hit the database until confirmation--not the experience I was
looking for.

If a user has a confirmed email in the database, it will stay in the
database until the new one has been confirmed.

Removed some debug print statements.
Merge branch 'master' into email-confirmation

Fixes #11
Addressed feedback/fixed email clearing
Fix reminders
Merge pull request #14 from brandonsato/email-confirmation

Implements email confirmation