Properly show middlewares on rake about.

railties/builtin/rails_info/rails/info.rb

@@ -51,9 +51,12 @@ module Rails
 
       def to_s
         column_width = properties.names.map {|name| name.length}.max
-        ["About your application's environment", *properties.map do |property|
-          "%-#{column_width}s   %s" % property
-        end] * "\n"
+        info = properties.map do |name, value|
+          value = value.join(", ") if value.is_a?(Array)
+          "%-#{column_width}s   %s" % [name, value]
+        end
+        info.unshift "About your application's environment"
+        info * "\n"
       end
 
       alias inspect to_s