Fixed bug caused by 'postgres'.classify returning 'Postgre'

* String#classify should not be used anyway. DM gems are trying to
  stay away from using any monkey patched methods when at all possible.
  This allows us to cherry pick in the minimal number of methods from
  AS, polluting the least amount of ruby core/stdlib gems.

  I realize this is somewhat futile with dm-rails, given that it will
  run inside Rails and have the full AS gem required. If any of this
  code is extracted into a dm-config base gem, then this approach
  *will* make things easier working with other frameworks.

lib/dm-rails/setup.rb

@@ -32,7 +32,7 @@ def self.setup_log_listener(adapter_name)
         # FIXME Setting DataMapper::Logger.new($stdout, :off) alone won't work because the #log
         # method is currently only available in DO and needs an explicit DO Logger instantiated.
         # We turn the logger :off because ActiveSupport::Notifications handles displaying log messages
-        do_adapter = DataObjects.const_get(adapter_name.classify)
+        do_adapter = DataObjects.const_get(ActiveSupport::Inflector.camelize(adapter_name))
         do_adapter.logger = DataObjects::Logger.new($stdout, :off)
       end
     end