Update the installation guide for v2.0.0
Update the installation guide for v2.0.0

ktnyt/chainer,ktnyt/chainer,okuta/chainer,chainer/chainer,chainer/chainer,hvy/chainer,kashif/chainer,ktnyt/chainer,ktnyt/chainer,keisuke-umezawa/chainer,okuta/chainer,okuta/chainer,rezoo/chainer,niboshi/chainer,anaruse/chainer,wkentaro/chainer,pfnet/chainer,tkerola/chainer,keisuke-umezawa/chainer,chainer/chainer,jnishi/chainer,aonotas/chainer,chainer/chainer,hvy/chainer,okuta/chainer,jnishi/chainer,kiyukuta/chainer,wkentaro/chainer,niboshi/chainer,jnishi/chainer,ronekko/chainer,keisuke-umezawa/chainer,niboshi/chainer,wkentaro/chainer,delta2323/chainer,hvy/chainer,wkentaro/chainer,niboshi/chainer,jnishi/chainer,hvy/chainer,ysekky/chainer,keisuke-umezawa/chainer