Added a reminder email feature to shifts view and model
Merge branches 'feature/reminderEmail' and 'master'
Add delayed_job gem to schedule email jobs, remove sendgrid tag from landing page, change notifier method.
Update configuration settings to work with heroku and sendgrid.
Add default heroku email to shift notify.
Add reminder to shifts such that on creation an email is sent to remind volunteers of their shifts.
Add migration for email field, and add email text to email view.
Fix merge conflicts.