make react a peer dependency - closes #35

Author: MicheleBertoli

package.json

@@ -51,7 +51,9 @@
     ]
   },
   "dependencies": {
-    "object-assign": "^4.0.1",
+    "object-assign": "^4.0.1"
+  },
+  "peerDependencies": {
     "react": "^0.14.2",
     "react-dom": "^0.14.2"
   }