Merge pull request chainer#6383 from kmaehashi/release-v6.0.0b3

Bump version to v6.0.0b3

Merge pull request chainer#6382 from asi1024/v5

Bump version number to v5.3.0

Merge pull request chainer#6077 from asi1024/v6.0.0b2

Bump version to v6.0.0b2

Merge pull request chainer#6078 from kmaehashi/release-v5.2.0

Bump version number to v5.2.0

Merge pull request chainer#5743 from chainer/chainerx-docs

Build ChainerX documentation on ReadTheDocs

Merge pull request chainer#5758 from chainer/release-v5.1.0

Bump version to v5.1.0

Merge pull request chainer#5579 from kmaehashi/release-v6.0.0a1

Bump version to v6.0.0a1

Merge pull request chainer#5581 from hvy/update-v5.0.0

Update to v5.0.0

Merge pull request chainer#5390 from kmaehashi/bump-v5.0.0rc1-docker

Bump docker image and fix docs for iDeep 2.x support

Merge pull request chainer#5393 from kmaehashi/bump-v4.5.0-docker

Bump version in Dockerfiles to v4.5.0