Backwards compatibility with old Rack aPI. Fixes #447

middleman-core/lib/middleman-core/core_extensions/request.rb

@@ -23,6 +23,8 @@ module Middleman
           app.extend ClassMethods
           app.extend ServerMethods
           
+          Middleman.extend CompatibleClassMethods
+      
           # Include instance methods
           app.send :include, InstanceMethods
         end
@@ -135,6 +137,18 @@ module Middleman
         end
       end
       
+      module CompatibleClassMethods
+        # Create a new Class which is based on Middleman::Application
+        # Used to create a safe sandbox into which extensions and
+        # configuration can be included later without impacting
+        # other classes and instances.
+        #
+        # @return [Class]
+        def server(&block)
+          ::Middleman::Application.server(&block)
+        end
+      end
+
       # Methods to be mixed-in to Middleman::Application
       module InstanceMethods
         # Backwards-compatibility with old request.path signature