exercism/exercism.io — pull request #1155 by Tonkpils (2013-12-14 04:11:46+00:00)
Title: Adding unique index on team slug.

A validation at the model level might not be enough to prevent duplicate records in the db. Adding unique index fixes this case.

@jdiago pointed this out for me. I'm committing it for him.

This possibly fixes #1150