Pluralise user_preferences_controller

This is the rails convention for controllers and can make route
generation easier.

http://guides.rubyonrails.org/action_controller_overview.html#controller-naming-convention

test/controllers/user_preferences_controller_test.rb

@@ -1,28 +1,28 @@
 require "test_helper"
 
-class UserPreferenceControllerTest < ActionController::TestCase
+class UserPreferencesControllerTest < ActionController::TestCase
   ##
   # test all routes which lead to this controller
   def test_routes
     assert_routing(
       { :path => "/api/0.6/user/preferences", :method => :get },
-      { :controller => "user_preference", :action => "read" }
+      { :controller => "user_preferences", :action => "read" }
     )
     assert_routing(
       { :path => "/api/0.6/user/preferences", :method => :put },
-      { :controller => "user_preference", :action => "update" }
+      { :controller => "user_preferences", :action => "update" }
     )
     assert_routing(
       { :path => "/api/0.6/user/preferences/key", :method => :get },
-      { :controller => "user_preference", :action => "read_one", :preference_key => "key" }
+      { :controller => "user_preferences", :action => "read_one", :preference_key => "key" }
     )
     assert_routing(
       { :path => "/api/0.6/user/preferences/key", :method => :put },
-      { :controller => "user_preference", :action => "update_one", :preference_key => "key" }
+      { :controller => "user_preferences", :action => "update_one", :preference_key => "key" }
     )
     assert_routing(
       { :path => "/api/0.6/user/preferences/key", :method => :delete },
-      { :controller => "user_preference", :action => "delete_one", :preference_key => "key" }
+      { :controller => "user_preferences", :action => "delete_one", :preference_key => "key" }
     )
   end