Make release build the default
Make release build the default

jnishi/chainer,chainer/chainer,hvy/chainer,wkentaro/chainer,wkentaro/chainer,keisuke-umezawa/chainer,jnishi/chainer,ktnyt/chainer,keisuke-umezawa/chainer,chainer/chainer,keisuke-umezawa/chainer,jnishi/chainer,tkerola/chainer,hvy/chainer,chainer/chainer,niboshi/chainer,niboshi/chainer,okuta/chainer,chainer/chainer,keisuke-umezawa/chainer,jnishi/chainer,okuta/chainer,okuta/chainer,ktnyt/chainer,ktnyt/chainer,hvy/chainer,niboshi/chainer,wkentaro/chainer,ktnyt/chainer,hvy/chainer,niboshi/chainer,pfnet/chainer,okuta/chainer,wkentaro/chainer