Reset password instructions (via email)

* Added lines to development, production, test.rb to set up mailer.
  * Currently uses noreplygorillaapp@gmail.com as sending email address, this can be changed later.
* Added a total of 12 tests for all password reset-ty things
  * Tests that views / buttons / links redirect you to correct page / return correct error messages / behave appropriately
  * Tests password reset token resets appropriately
  * Tests reset_password! method works
  * Final test goes through entire process of creating user, sending reset instructions, accessing the custom url based on the password reset token, filling in the new password, signing out and logging back in with the new password.