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

Merge pull request chainer#5265 from asi1024/release-v5.0.0b4

Update version numbers in Dockerfiles

Merge pull request chainer#5264 from mitmul/fix-version-number

Update version numbers to v4.4.0

Merge pull request chainer#5156 from kmaehashi/release-v4.3.1-dockerfile

Update dockerfiles to use v4.3.1

Merge pull request chainer#5112 from kmaehashi/release-v5.0.0b3

Bump version to v5.0.0b3

Merge pull request chainer#5116 from kmaehashi/release-v4.3.0-dockerfile

Bump chainer version in Dockerfile to v4.3.0

Merge pull request chainer#4976 from kmaehashi/release-v5.0.0b2

[skip ci] Bump version to v5.0.0b2