Use explicit files whitelist

Author: gaearon

.npmignore

@@ -12,6 +12,10 @@
     "test:cov": "babel-node ./node_modules/.bin/isparta cover ./node_modules/.bin/_mocha -- --recursive",
     "prepublish": "npm run lint && npm run test && npm run clean && npm run build"
   },
+  "files": [
+    "lib",
+    "src"
+  ],
   "repository": {
     "type": "git",
     "url": "https://github.com/gaearon/redux-devtools.git"