run OS X test only on master/stable branch to avoid delay
run OS X test only on master/stable branch to avoid delay

pfnet/chainer,chainer/chainer,ktnyt/chainer,niboshi/chainer,tkerola/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,niboshi/chainer,niboshi/chainer,anaruse/chainer,jnishi/chainer,jnishi/chainer,wkentaro/chainer,hvy/chainer,chainer/chainer,hvy/chainer,jnishi/chainer,chainer/chainer,hvy/chainer,keisuke-umezawa/chainer,okuta/chainer,okuta/chainer,wkentaro/chainer,hvy/chainer,rezoo/chainer,niboshi/chainer,keisuke-umezawa/chainer,wkentaro/chainer,aonotas/chainer,wkentaro/chainer,ktnyt/chainer,ktnyt/chainer,jnishi/chainer,ronekko/chainer,chainer/chainer,okuta/chainer,ktnyt/chainer,okuta/chainer