Revert "With the release of Rails 4, Rails 3.0 and 3.1 are no longer supported"

This reverts commit 42b14892321e42a9c41725378b5f57172a9663b0.

Conflicts:
	.travis.yml
	Gemfile
Merge pull request #695 from collectiveidea/bring-back-3

Bring back 3.0