Merge pull request chainer#327 from pfnet/v1.2.0

v1.2.0

Merge pull request chainer#291 from pfnet/v1.1.2

v1.1.2

Merge pull request chainer#251 from pfnet/v1.1.1

v1.1.1

Merge pull request chainer#81 from pfnet/v1.0.1

v1.0.1

Fix computation graph to computational graph