Prepare Travis to run RSpec and Jasmine tests.

+ Source: http://about.travis-ci.org/docs/user/gui-and-headless-browsers/
Add .env file for Travis.
Add default sender to action mailer.

+ Hopefully this will satisfy Travis to run the specs.
Attempt to fix Travis error message.

+ Travis states "A sender (Return-Path, Sender or From) required
  to send a message" when a user is created.
Remove deprecated default_sender property from action mailer.