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


Guys I know very little about regex but I noticed the issue while working on a Spree upgrade and traced the issue down to #191 which took me to the discussions on rails/rails so I believe the change makes sense. I've run the tests against rails 4.0.0.rc1 and everything passes.