Add tests for enrollment validation event creation.

Also change event_output to tuple_output, and make event output the
default.  (Tuple output is still the primary output format for tests.)

Trigger a student_courseenrollment dump when interval includes today.

Add EnrollmentValidationWorkflow to combine a dump and validation.
Add acceptance test.
Merge pull request #41 from edx/brian/synth-test

Add EnrollmentValidationWorkflow.