package.json: fix "main" to point to right file

package.json

@@ -2,7 +2,7 @@
   "name": "test-redux-goodies",
   "version": "0.0.2",
   "description": "Helpers to test Redux code.",
-  "main": "lib/index.js",
+  "main": "lib/node.js",
   "scripts": {
     "build": "babel src --presets es2015 --out-dir lib",
     "test": "echo \"Error: no test specified\" && exit 1"