Switch Grape::API's @setup var to an Array (from a Set)

Author: Haerezis

lib/grape/api.rb

@@ -40,7 +40,7 @@ def inherited(api)
       # an instance that will be used to create the set up but will not be mounted
       def initial_setup(base_instance_parent)
         @instances = []
-        @setup = Set.new
+        @setup = []
         @base_parent = base_instance_parent
         @base_instance = mount_instance
       end