Remove ActiveSupport::OrderedHash usage.

Minus one ActiveSupport dependency!
OrderedHash is a hash that preserves insertion order. It's a legacy
stuff since Ruby >= 1.9 already preserves insertion order.

lib/grape.rb

@@ -9,7 +9,6 @@
 require 'set'
 require 'active_support/version'
 require 'active_support/core_ext/hash/indifferent_access'
-require 'active_support/ordered_hash'
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/hash/deep_merge'

lib/grape/dsl/configuration.rb

@@ -98,7 +98,7 @@ def unset_description_field(field)
       # Merge multiple layers of settings into one hash.
       def stacked_hash_to_hash(settings)
         return nil if settings.nil? || settings.blank?
-        settings.each_with_object(ActiveSupport::OrderedHash.new) { |value, result| result.deep_merge!(value) }
+        settings.each_with_object({}) { |value, result| result.deep_merge!(value) }
       end
 
       # Returns an object which configures itself via an instance-context DSL.

lib/grape/util/content_types.rb

@@ -1,18 +1,18 @@
 module Grape
   module ContentTypes
     # Content types are listed in order of preference.
-    CONTENT_TYPES = ActiveSupport::OrderedHash[
-                    :xml, 'application/xml',
-                    :serializable_hash, 'application/json',
-                    :json, 'application/json',
-                    :binary, 'application/octet-stream',
-                    :txt, 'text/plain'
-   ]
+    CONTENT_TYPES = {
+      xml: 'application/xml',
+      serializable_hash: 'application/json',
+      json: 'application/json',
+      binary: 'application/octet-stream',
+      txt: 'text/plain'
+    }
 
     def self.content_types_for_settings(settings)
       return nil if settings.nil? || settings.blank?
 
-      settings.each_with_object(ActiveSupport::OrderedHash.new) { |value, result| result.merge!(value) }
+      settings.each_with_object({}) { |value, result| result.merge!(value) }
     end
 
     def self.content_types_for(from_settings)

spec/grape/api_spec.rb

@@ -2812,10 +2812,10 @@ def serializable_hash
       end
       it 'hash' do
         subject.get '/example' do
-          ActiveSupport::OrderedHash[
-            :example1, 'example1',
-            :example2, 'example2'
-        ]
+          {
+            example1: 'example1',
+            example2: 'example2'
+          }
         end
         get '/example'
         expect(last_response.status).to eq(200)