Revert "Herokuでだけ1.9.3決め打ちにする"

This reverts commit 68d928ed7f51fc28bce4be0170504015a372be8f.
This does not work in heroku
Merge pull request #45 from sanemat/feature/heroku

Revert "Herokuでだけ1.9.3決め打ちにする"