implement assignment normalisation

especially when the value is a send that needs normalising
fixes several broken tests

test/vool/normalization/test_assignment.rb

@@ -0,0 +1,42 @@
+require_relative "helper"
+
+module Vool
+  module Norm
+
+    class TestAssignSend < NormTest
+      def setup
+        super
+        @stm = normalize("a = foo(1 - 2)")
+      end
+      def test_many
+        assert_equal Statements , @stm.class
+      end
+      def test_assignment
+        assert_equal LocalAssignment , @stm.first.class
+      end
+      def test_assignment_value
+        assert_equal SendStatement , @stm.first.value.class
+      end
+      def test_assignment_method
+        assert_equal :- , @stm.first.value.name
+      end
+      def test_length
+        assert_equal 2 , @stm.length
+      end
+      def test_name
+        assert @stm.first.name.to_s.start_with?("tmp_") , @stm.first.name
+      end
+      def test_assignment2
+        assert_equal LocalAssignment , @stm.last.class
+      end
+      def test_name
+        assert_equal :a , @stm.last.name
+      end
+      def test_assignment_method2
+        assert_equal :foo , @stm.last.value.name
+      end
+
+    end
+
+  end
+end