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.
Removed conditional based on incorrect assumption (that a question's randomization cannot be changed) to fix variant bug

Removed initialization of unused variable

Updated test cases to reflect new behavior

Added additional test case for different answer variants with most recent empty and a reference in AUTHORS
Add acceptance test.
Merge pull request #41 from edx/brian/synth-test

Add EnrollmentValidationWorkflow.
Merge pull request #40 from edx/dylanrhodes/answer-variant-switch-fix

Incorrect variant for answer distribution bug fix
Update database exporter acceptance test.
Merge pull request #43 from rocha/fix-exporter-acceptance-test

Update database exporter acceptance test.
Refactor daily course enrollment
Renamed table tasks