Merge pull request #591 from muupan/update_to_v0.8.0

Update the version to 0.8.0

Merge pull request #489 from toslunar/fix-to_factorized_noisy

Make `to_factorized_noisy` work with sequential links

Merge pull request #406 from chainer/update-to-v0.6

Update the version to v0.6

Merge pull request #354 from prabhatnagarajan/grammar_nit

nit on grammar of a comment:

Merge pull request #289 from chainer/update-version-v0.4

Update to v0.4

Merge pull request #199 from chainer/muupan-patch-4

Update to v0.3.0

Merge pull request #106 from chainer/muupan-patch-1

Update to v0.2.0

Merge pull request #57 from muupan/pcl-prioritized-replay

Use Prioritized Replay for PCL