support Sphinx 2.0 and use absolute path to support the latest RTD
support Sphinx 2.0 and use absolute path to support the latest RTD

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