Revert dot scaping in SQL values

Which was added in #191 to fix a issue present in Rails < 4. However
that fix is no longer necessary since Rails 4 deals properly with dots
in SQL. See these for details:

  https://github.com/rails/rails/issues/9055
  https://github.com/rails/rails/commit/a2dab46

This would be a query generated in Rails 3.2.13:

  "SELECT \"spree_users\".* FROM \"spree_users\"
    WHERE (\"spree_users\".\"email\" LIKE
'spree_commerce@example.com%')"

While on Rails 4.0.0.rc1 it would be generated like this:

  "SELECT \"spree_users\".* FROM \"spree_users\"
    WHERE (\"spree_users\".\"email\" LIKE
'spree_commerce@example\\.com%')"

and so return unexpected results