Allow React 16 as peerDependency for 4.x (#660)

Author: gaearon

package.json

@@ -95,7 +95,7 @@
     "loose-envify": "^1.1.0"
   },
   "peerDependencies": {
-    "react": "^0.14.0 || ^15.0.0-0 || ^15.4.0-0",
+    "react": "^0.14.0 || ^15.0.0-0 || ^15.4.0-0 || ^16.0.0-0",
     "redux": "^2.0.0 || ^3.0.0"
   },
   "browserify": {