#22 docs/variables.mdの初版翻訳
Merge pull request #51 from gosyujin/translate-variable-#22

#22 docs/variables.mdの初版翻訳
#26 docs/heroku.mdの初版翻訳
Merge pull request #52 from gosyujin/translate-heroku-#26

#26 docs/heroku.mdの初版翻訳