exercism/exercism.io — pull request #1846 by tbloncar (2014-09-25 05:47:29+00:00)
Title: Address duplicate team member bug. Fixes #1724.

Fixes duplicate recruits test and adds scoped uniqueness validation to
TeamMembership. Also adds guard to Team#recruit to remove existing
members from invitees. Performs this same subtraction when sending out
notifications in routes/teams.