Add a dedicated validator to allow entering multiple emails as recipient of the reminder
Let the send_reminder of the fedocal_cron return the messages that were sent

This is useful especially for test and debug purposes
Allow the cron job to send the reminder to multiple addresses in one go

Relates to https://fedorahosted.org/fedocal/ticket/134
Add a dedicated unit-test file to test the cron reminder
Add mock to the list of dependencies as it is used now in the tests
Small cleaning
Do not store spaces in the email address specified for the reminders

Fixes https://fedorahosted.org/fedocal/ticket/134
Cron tests require a real sqlite db, but at the end go back to the in-memory one
Add unit-tests testing the web UI for adding meetings with a reminder

These tests check the behavior of the web UI when the user adds a meeting
with a reminder and:
 a) the email to send the reminder to is invalid
 b) the reminder is sent to 1 email address
 c) the reminder is sent to 2 email addresses
Fix comment
Check the behavior of the web UI when one of the email address specified is invalid
Merge pull request #140 from fedora-infra/multi_email

Multi email