Migrating from heroku MySQL to PostgreSQL

Some others modifications was made:

- Migrating from nginx to apache on heroku
- Solving auto-deploy error
- Creating env file to heroku

An requirement when postgreSQL is used are added to the <code>composer.json</code> file too(<code>doctrine/dbal</code>)
I think @joecohens explained a reason for not putting it into dev-dependency?