Make react and react-dom peer dependencies (#20)

Author: MicheleBertoli

package.json

@@ -40,10 +40,12 @@
     "redux": "^3.5.2"
   },
   "dependencies": {
-    "react": "^0.14 || ^15.0.0-rc || ^15.0",
-    "react-dom": "^0.14 || ^15.0.0-rc || ^15.0",
     "react-notification-system": "^0.2.7"
   },
+  "peerDependencies": {
+    "react": "^0.14 || ^15.0.0-rc || ^15.0",
+    "react-dom": "^0.14 || ^15.0.0-rc || ^15.0"
+  },
   "browserify-shim": {
     "react": "global:React"
   },