Test runner: Detect extra property in 'actual' but not in 'expected'. (#407)

* Test runner: Detect extra property in 'actual' but not in 'expected'.

Also update all expected.json where this would result in errors.

* Include rmExpected.js script in case it is needed again

test/fixtures/experimental/async-generators/class-method-2/expected.json

@@ -90,7 +90,6 @@
                 }
               },
               "static": false,
-              "kind": "method",
               "computed": false,
               "key": {
                 "type": "Identifier",
@@ -109,6 +108,7 @@
                 },
                 "name": "a"
               },
+              "kind": "method",
               "id": null,
               "generator": true,
               "expression": false,