fixing the challenge_types def in the model
fixing the challenge_types def in the model

mvexel/maproulette,Crashfreak/maproulette,mvexel/mr-tnav,mvexel/maproulette,mvexel/maproulette,osmlab/maproulette,Crashfreak/maproulette,osmlab/maproulette,osmlab/maproulette,Crashfreak/maproulette,Crashfreak/maproulette,osmlab/maproulette,mvexel/maproulette,mvexel/mr-tnav