Do away with Blacklight::SearchBuilder

Using an included module instead of class inheritance.
This should make generating a custom SearchBuilder simpler as it doesn't
need to inherit from a implementation tightly coupled to Solr (or
something else).

lib/blacklight.rb

@@ -5,7 +5,6 @@ module Blacklight
   autoload :Configurable,          'blacklight/configurable'
   autoload :Configuration,         'blacklight/configuration'
   autoload :SearchFields,          'blacklight/search_fields'
-  autoload :SearchBuilder,         'blacklight/search_builder'
   autoload :SearchBuilderBehavior, 'blacklight/search_builder_behavior'
 
   autoload :Document, 'blacklight/document'

lib/blacklight/solr/search_builder.rb

@@ -1,5 +1,5 @@
 module Blacklight::Solr
-  class SearchBuilder < Blacklight::SearchBuilder
+  class SearchBuilder
     include SearchBuilderBehavior
   end
 end

lib/blacklight/solr/search_builder_behavior.rb

@@ -1,5 +1,6 @@
 module Blacklight::Solr
   module SearchBuilderBehavior
+    include Blacklight::SearchBuilderBehavior
     ####
     # Start with general defaults from BL config. Need to use custom
     # merge to dup values, to avoid later mutating the original by mistake.

spec/lib/blacklight/search_builder_spec.rb → spec/lib/blacklight/search_builder_behavior_spec.rb

@@ -1,10 +1,20 @@
 require 'spec_helper'
 
-describe Blacklight::SearchBuilder do
+describe Blacklight::SearchBuilderBehavior do
   let(:processor_chain) { [] }
   let(:blacklight_config) { Blacklight::Configuration.new }
   let(:scope) { double blacklight_config: blacklight_config }
-  subject { described_class.new processor_chain, scope }
+
+  before do
+    class TestBuilder
+      include Blacklight::SearchBuilderBehavior
+    end
+  end
+
+  after { Object.send(:remove_const, :TestBuilder) }
+
+  subject { TestBuilder.new processor_chain, scope }
+
   describe "#with" do
     it "should set the blacklight params" do
       params = {}