ensure that child usage does not manipulate cached template

lib/rabl-rails/compiler.rb

@@ -67,7 +67,7 @@ module RablRails
       name = options[:root] if options.has_key? :root
       if options[:partial]
         template = Library.instance.compile_template_from_path(options[:partial])
-        @template[name] = template.merge!(:_data => data)
+        @template[name] = template.merge(:_data => data)
       elsif block_given?
         @template[name] = sub_compile(data) { yield }
       end

lib/rabl-rails/template.rb

@@ -2,7 +2,7 @@ module RablRails
   class CompiledTemplate
     attr_accessor :source, :data, :root_name
 
-    delegate :[], :[]=, :merge!, :to => :source
+    delegate :[], :[]=, :merge!, :merge, :to => :source
 
     def initialize
       @source = {}

test/compiler_test.rb

@@ -113,6 +113,7 @@ class CompilerTest < ActiveSupport::TestCase
 
     t = @compiler.compile_source(%{child(:user, :partial => 'users/base') })
     assert_equal( {:user => { :_data => :user, :id => :id } }, t.source)
+    assert_equal( {:id => :id}, mock_template.source)
   end
 
   test "glue is compiled as a child but with anonymous name" do