Add instnace var assignment and access

lib/to_source/visitor.rb

@@ -26,6 +26,15 @@ def local_variable_access(node, parent)
       emit node.name
     end
 
+    def instance_variable_assignment(node, parent)
+      emit "%s = " % node.name
+      node.value.lazy_visit self, node
+    end
+
+    def instance_variable_access(node, parent)
+      emit node.name
+    end
+
     def fixnum_literal(node, parent)
       emit node.value.to_s
     end

test/to_source/visitor_test.rb

@@ -19,10 +19,18 @@ def test_local_assignment
       assert_source "foo = 1"
     end
 
+    def test_ivar_assignment
+      assert_source "@foo = 1"
+    end
+
     def test_local_access
       assert_source "foo = 1\nfoo"
     end
 
+    def test_ivar_access
+      assert_source "@foo"
+    end
+
     def test_constant_access
       assert_source "Rubinius"
     end