Merge pull request #188 from muupan/update-to-v0.4.0

Update to v0.4.0

Merge pull request #152 from pfnet/update-to-v0.3.0

Update to v0.3.0

Merge pull request #114 from pfnet/muupan-patch-1

Update the version to v0.2.1

Merge pull request #109 from pfnet/muupan-patch-1

Update the version in setup.py to 0.2.0

Make update_counter multiprocess safe (#30)