Add sms reminders.

Environment variables: encrypt for travis and add to config. Exclude
tests from running on travis.
Add task to fetch and send sms reminders
Add send sms reminders endpoint

Move test helper method for authentication somewhere reusable
Combine PostReminderSend tasks for each type
Combine module logic
Make send reminder base class abstract

Actually instantiate send reminder using child class
Add rake task to test sending sms