Tweaks for Rails 4

I loosened up the version string comparison.

````
      # In Rails3.2 method #extract_schema_and_table is moved into Utils module.
      # In Rails3.1 it's implemented right in PostgreSQLAdapter class.
      # For everything after Rails3.2 we include the module into PostgreSQLAdapter in order to make
      # it compatible to Rails3.1
      # -- sergey.potapov 2012-06-25
      if ActiveRecord::VERSION::STRING >= '3.2'
        include self::Utils
      end
````

EDIT 1: Also another tweak to fix an error when attempting to cast the ActiveRecord::Result as a Hash.