Merge pull request #228 from javascript-obfuscator/target-es2017-tests

Updated ts target in tests

tsconfig.test.json

@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
     "outDir": "test-tmp",
-    "target": "es6",
+    "target": "es2017",
     "lib": [
       "es2017",
       "dom"
@@ -22,4 +22,4 @@
   "exclude": [
     "node_modules"
   ]
-}
+}