Revise according to review comments

    * Comments should use hashes not triple quoted strings
    * The data should already be sorted, and does not need to be sorted again
    * As a result, all of the expected indexes had to be switched
    * Add beforeyesterday data value to test_date_delta_with_no_constraints
    * Change docstring for test_date_delta_with_no_constraints
https://github.com/mozilla/fjord/pull/319