[GEM] Update Rails version to 4.1.0
Replace db:test:preapre task with ActiveRecord::Migration.maintain_test_schema!

as of Rails 4.1.0

Reference: https://github.com/rails/rails/blob/4-1-stable/railties/CHANGELOG.md
Merge pull request #20 from Jarviis/rails-4.1

[GEM] Update Rails version to 4.1.0