Include Predications in Grouping

Also, removed unused ordering.rb file, since it is identical
to the one being created in unary.rb already, and isn't
required anywhere.

lib/arel/nodes.rb

@@ -13,6 +13,7 @@ require 'arel/nodes/false'
 
 # unary
 require 'arel/nodes/unary'
+require 'arel/nodes/grouping'
 require 'arel/nodes/ascending'
 require 'arel/nodes/descending'
 require 'arel/nodes/unqualified_column'

lib/arel/nodes/grouping.rb

@@ -0,0 +1,7 @@
+module Arel
+  module Nodes
+    class Grouping < Unary
+      include Arel::Predications
+    end
+  end
+end

lib/arel/nodes/ordering.rb

@@ -1,6 +0,0 @@
-module Arel
-  module Nodes
-    class Ordering < Unary
-    end
-  end
-end

lib/arel/nodes/unary.rb

@@ -12,7 +12,6 @@ module Arel
     %w{
       Bin
       Group
-      Grouping
       Having
       Limit
       Not

test/nodes/test_grouping.rb

@@ -0,0 +1,13 @@
+require 'helper'
+
+module Arel
+  module Nodes
+    describe 'Grouping' do
+      it 'should create Equality nodes' do
+        grouping = Grouping.new('foo')
+        grouping.eq('foo').to_sql.must_be_like %q{('foo') = 'foo'}
+      end
+    end
+  end
+end
+