Update to test against Rails 5.1

Gemfile

@@ -31,6 +31,7 @@ else
     gem 'responders', '~> 2.0'
     gem 'sass-rails', '>= 5.0'
     gem 'coffee-rails', '~> 4.1.0'
+    gem 'json', '~> 1.8'
   when /^4.[01]/
     gem 'sass-rails', '< 5.0'
   end

app/helpers/blacklight_advanced_search/advanced_helper_behavior.rb

@@ -32,7 +32,7 @@ def select_menu_for_field_operator
     # Current params without fields that will be over-written by adv. search,
     # or other fields we don't want.
     def advanced_search_context
-      my_params = params.except :page, :commit, :f_inclusive, :q, :search_field, :op, :action, :index, :sort, :controller, :utf8
+      my_params = search_state.params_for_search.except :page, :f_inclusive, :q, :search_field, :op, :index, :sort
 
       my_params.except!(*search_fields_for_advanced_search.map { |_key, field_def| field_def[:key] })
     end

lib/blacklight_advanced_search/engine.rb

@@ -2,5 +2,6 @@
 
 module BlacklightAdvancedSearch
   class Engine < Rails::Engine
+    require 'jquery-rails'
   end
 end