Ineffective org membership verification

[paxan]

I've noticed that org members that were not publicizing their membership were S.O.L.

They get this error:

The problem goes away once they hit "Publicize membership" button for themselves on the org members page. So that's the good news: we have the workaround.

I believe that a more appropriate way to check membership is
GET /orgs/:org/members/:user as described in Organization Members API. Then you'd display "the day the music stopped..." error if response status is other than 204.

I am running Play off v3 branch, FYI.