run e2e on travis

.travis.yml

   - rm -rf $HOME/.gradle/caches/*/plugin-resolution/
 
 install:
-  - java -version
   - nvm install $NODE_VERSION
   - curl -o- -L https://yarnpkg.com/install.sh | bash
   - yarn config set cache-folder $YARN_CACHE
   - yarn run lint
   - yarn run test-js
   - yarn run test-android
-  #- yarn run test-ios
+  - yarn run test-ios
   - yarn run release
   - set +e
 

scripts/test.ios.js

 
 function run() {
   process.chdir('./playground');
+  exec.execSync(`hardlink node_modules/react-native-navigation/ -u || true`);
+  exec.execSync(`yarn install`);
+  exec.execSync(`yarn run e2e release`);
   process.chdir('../');
 }