Add --allow-root to Bower

[charyorde]

Please add --allow-root to Bower script execution.

I'm getting Script cd public/assets/js && bower update && cd ../../.. handling the post-install-cmd event returned with an error during composer install

Version
1.3.0

[ryasmi]

Thanks for the issue, feel free to make a pull request :) be sure to reference this issue in the PR.