Update project to use PostgreSQL and Docker configuration for deployment using Heroku

[Riasy7]

Description of tasks for deployment:

Update Gemfile

• remove sqlite3 gem
• add pg gem

Update database configs

• configure postgresql settings with env variables (development, test, and production)

Dockerfile

• ensure dockerfile includes all packages necessary for running the application

Potentially create a .env file

• set up all the env variables of db connection (user, pass, host, port)

Potentially configure "Secrets"

• make sure credentials are in environment variables and are not committed to the repository

Run bundle before deploying

• update Gemfile.lock

Set up Heroku continuous deployment

• make sure all configs are ready first

Test Locally

• test the postgresql db connections
• test in deployment and production environments

Finally deploy Real Ratings for continuous deployment!