Don't add to 'all' team unless actually necessary

This rewrite does better at avoiding the awful race-condition where we
might add someone to the 'all' team immediately after they've been
removed from the Org. We check org-membership /after/ we've established
they're not in the 'all' team, and then add the user immediately, only if
they /are/ a member of the Org.

Note that membership of the 'all' team implies membership of the Org, so
no need to do the `user.isMemberOf(org)` call if the user is already a
member of the team.

hub4j/github-api#75

app/lib/Implicits.scala

@@ -18,9 +18,11 @@ object Implicits {
     lazy val allTeam = org.getTeams()("all")
 
     def testMembership(user: GHUser): Boolean = {
-      val isMemberOfOrg = user.isMemberOf(org)
-      if (isMemberOfOrg) { allTeam.add(user) }
-      isMemberOfOrg
+      if (user.isMemberOf(allTeam)) true else {
+        val orgMember = user.isMemberOf(org)
+        if (orgMember) { allTeam.add(user) }
+        orgMember
+      }
     }
   }