Translated mongo docs.
/classes/session/usage.html 概要一部翻訳
Translation of installation/upgrade.html
Merge pull request #151 from inouet/1.5/develop_japanese

Translated mongo docs.
Merge pull request #152 from egmc/patch-1

/classes/session/usage.html 概要一部翻訳
Merge pull request #153 from koyhoge/feature/installationo-upgrade

Translation of installation/upgrade.html
Update CREDITS.md
Update packages/email/usage.html
Merge pull request #154 from ounziw/patch-1

Update CREDITS.md
Merge pull request #155 from orcaaoshi/patch-7

Update packages/email/usage.html