THRIFT-4653: ES6 classes support (apache#1615)

* ES6 classes support
* Lint generated code
* ES6 Tests for NodeJS
* Add eslint rules for nodejs
* Run prettier/eslint on nodejs test code

.eslintignore

@@ -0,0 +1,9 @@
+# TODO: Use eslint on js lib and generated code
+
+# Ignore lib/js for now, which uses jshint currently
+lib/js/*
+# Ignore all generated code for now
+**/gen-*
+
+# Don't lint nested node_modules
+**/node_modules

.eslintrc.json

@@ -0,0 +1,24 @@
+{
+  "env": {
+    "es6": true,
+    "node": true
+  },
+  "extends": [
+    "eslint:recommended",
+    "plugin:prettier/recommended"
+  ],
+  "parserOptions": {
+    "ecmaVersion": 2017
+  },
+  "rules": {
+    "no-console": "off",
+    "no-var": "error",
+    "prefer-const": "error",
+    "no-constant-condition": [
+      "error",
+      {
+        "checkLoops": false
+      }
+    ]
+  }
+}