Only include production files in npm releases

Author: lukechilds

package.json

@@ -3,6 +3,10 @@
   "version": "2.0.0-prerelease",
   "description": "The assert module from Node.js, for the browser.",
   "main": "build/assert.js",
+  "files": [
+    "build/assert.js",
+    "build/internal"
+  ],
   "license": "MIT",
   "homepage": "https://github.com/browserify/commonjs-assert",
   "repository": "browserify/commonjs-assert",