third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/js/package.json

 {
   "name": "google-protobuf",
-  "version": "3.0.0-alpha.6",
+  "version": "3.1.0",
   "description": "Protocol Buffers for JavaScript",
   "main": "google-protobuf.js",
-  "dependencies": {
+  "files": [
+    "google"
+  ],
+  "dependencies": {},
+  "devDependencies": {
+    "glob": "~6.0.4",
+    "google-closure-compiler": "~20160619.0.0",
     "google-closure-library": "~20160125.0.0",
     "gulp": "~3.9.0",
     "jasmine": "~2.4.1"
   },
-  "devDependencies": {
-    "google-closure-compiler": "~20151216.2.0",
-    "glob": "~6.0.4"
-  },
   "scripts": {
     "test": "node ./node_modules/gulp/bin/gulp.js test"
   },
   "repository": {
     "type": "git",
     "url": "https://github.com/google/protobuf/tree/master/js"
   },
-  "author": "",
+  "author": "Google Protocol Buffers Team",
   "license": "Apache-2.0"
 }