regenerate package.json to add README

Less `WARN` running `npm install`, and the diff:
```
-  }
+  },
+  "gitHead": "a26f298b69220eb22996cf02391710f32c4615c4",
+  "readmeFilename": "README.md",
+  "directories": {
+    "test": "test"
+  },
+  "license": "BSD"
```