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
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.
Define AnswerDistributionWorkflow.

Combines AnswerDistributionOneFilePerCourseTask and
AnswerDistributionToMySQLTaskWorkflow into a single workflow.
Merge pull request #44 from edx/brian/answer-dist-all

Define AnswerDistributionWorkflow.