Remove code supporting Rails 4.0 and earlier

app/helpers/blacklight/url_helper_behavior.rb

@@ -287,10 +287,4 @@ def remove_facet_params(field, item, source_params=params)
   def bookmarks_export_url(format, params = {})
     bookmarks_url(params.merge(format: format, encrypted_user_id: encrypt_user_id(current_or_guest_user.id) ))
   end
-
-  if ::Rails.version < "4.0"
-    def asset_url *args
-      "#{request.protocol}#{request.host_with_port}#{asset_path(*args)}"
-    end
-  end
 end

lib/blacklight/configuration.rb

@@ -304,26 +304,17 @@ def add_field_configuration_to_solr_request! *fields
     # Provide a 'deep copy' of Blacklight::Configuration that can be modifyed without affecting
     # the original Blacklight::Configuration instance.
     #
-    # The Rails 3.x version only copies hashes, and ignores arrays and similar structures
-    if ::Rails.version < "4.0"
-      def deep_copy
-        Marshal.load(Marshal.dump(self))
-      end
-      alias_method :inheritable_copy, :deep_copy
-    else
-      ##
-      # Rails 4.x provides `#deep_dup`, but it aggressively `#dup`'s class names
-      # too. These model names should not be `#dup`'ed or we might break ActiveModel::Naming.
-      def deep_copy
-        deep_dup.tap do |copy|
-          %w(repository_class response_model document_model document_presenter_class search_builder_class facet_paginator_class).each do |klass|
-            # Don't copy if nil, so as not to prematurely autoload default classes
-            copy.send("#{klass}=", send(klass)) unless fetch(klass.to_sym, nil).nil?
-          end
+    # Rails 4.x provides `#deep_dup`, but it aggressively `#dup`'s class names
+    # too. These model names should not be `#dup`'ed or we might break ActiveModel::Naming.
+    def deep_copy
+      deep_dup.tap do |copy|
+        %w(repository_class response_model document_model document_presenter_class search_builder_class facet_paginator_class).each do |klass|
+          # Don't copy if nil, so as not to prematurely autoload default classes
+          copy.send("#{klass}=", send(klass)) unless fetch(klass.to_sym, nil).nil?
         end
       end
-      alias_method :inheritable_copy, :deep_copy
     end
+    alias_method :inheritable_copy, :deep_copy
 
     ##
     # Get a view configuration for the given view type

lib/blacklight/facet_paginator.rb

@@ -17,12 +17,8 @@ class FacetPaginator
       { sort: :'facet.sort', page: :'facet.page', prefix: :'facet.prefix' }
     end
 
-    if Rails.version < "4.1"
-      self.request_keys = { sort: :'facet.sort', page: :'facet.page', prefix: :'facet.prefix' }
-    end
-
     attr_reader :offset, :limit, :sort, :prefix
-    
+
     # all_facet_values is a list of facet value objects returned by solr,
     # asking solr for n+1 facet values.
     # options: