remap UpdateExpression in module exports - closes #334

test/fixtures/transformation/es6-modules-system/remap/actual.js

@@ -1,7 +1,9 @@
 export var test = 2;
 test = 5;
+test++;
 
 (function () {
   var test = 2;
   test = 3;
+  test++;
 })();

test/fixtures/transformation/es6-modules-system/remap/expected.js

@@ -5,12 +5,14 @@ System.register("es6-modules-system/remap/expected", [], function (_export) {
       "use strict";
 
       var test = _export("test", 2);
-      test = 5;
+      _export("test", test = 5);
+      _export("test", test += 1);
 
       (function () {
         var test = 2;
         test = 3;
+        test++;
       })();
     }
   };
-});
+});