For reference, that .gitignore file can be found here:
/bootstrap/compiled.php
/vendor
composer.phar
composer.lock # Remove this one after you create a project
.env.*.php
.env.php
.DS_Store
Thumbs.db
As noted in the below comment, you probably want to commit composer.lock in your project. Laravel ignores it by default so the authors of the laravel/laravel package don't accidently impose packages on you.
Your project should include the composer.lock file so you can install packages of stable versions (via composer install instead of composer update) properly in your production environments.