Add subject lookup rake task.
Add task to clear storage for an experiment after it has been wrapped up.
Move memory storage test to separate test file
Add removing of subjects, so the will be re-assigned later.
Add rake tasks to manually assign, disqualify, and remove assignments of subjects.
Allow overwriting of assignments in Redis.
Rename remove to remove_assignment.
Code-review related cleanup.
Merge pull request #9 from Shopify/rake_tasks

Rake tasks to administer experiments