Be explicit about all npm package files

We were previously just globbing the entire google/ dir, which brings
in different versions of files that we don't normally publish to
npm. For example, we usually publish any_pb.js, which uses commonjs
requires instead of any.js, which uses closure's goog.require.

Author: dibenede

package.json

@@ -4,8 +4,13 @@
   "description": "Protocol Buffers for JavaScript",
   "main": "google-protobuf.js",
   "files": [
-    "google",
-    "LICENSE-asserts.md"
+    "google/protobuf/*_pb.js",
+    "google/protobuf/compiler/*_pb.js",
+    "google-protobuf.js",
+    "LICENSE.md",
+    "LICENSE-asserts.md",
+    "package.json",
+    "README.md"
   ],
   "dependencies": {},
   "devDependencies": {