Revert "trying to fix travis"

This reverts commit f62cce4897.

.travis.yml

   - yarn run test-js
   - yarn run test-android
   - yarn run test-ios
-  - cd playground && yarn run e2e release
   - yarn run release
   - set +e
 

scripts/test.ios.js

 const exec = require('shell-utils').exec;
 
 function run() {
-  exec.execSync(`cd playground && hardlink node_modules/react-native-navigation/ -u || true`);
-  exec.execSync(`cd playground && yarn install`);
-  //exec.execSync(`cd playground && yarn run e2e release`);
+  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('../');
 }
 
 run();