chore(deps): update React Native to 0.21.0

Author: marclaval

package.json

@@ -36,7 +36,7 @@
  "dependencies": {
  "angular2": "2.0.0-beta.8",
  "hammerjs": "2.0.6",
- "react-native": "0.20.0",
+ "react-native": "0.21.0",
  "reflect-metadata": "0.1.2",
  "rxjs": "5.0.0-beta.2",
  "zone.js": "0.5.15",