Add db:create and db:drop for MySQL/Postgres 🎊

[aledalgrande]

Needed for a better dev experience. I didn't use sequelize because it doesn't have support for opening a connection without a database, but the dialect libraries work.

Feel free to request any changes.

Solves #70.

[mention-bot]

@aledalgrande, thanks for your PR! By analyzing the history of the files in this pull request, we identified @Americas, @leebenson and @fossamagna to be potential reviewers.

[dagumak]

I was surprised to find that this was missing! @eseliger Thoughts?

[dagumak]

@aledalgrande

$ sequelize db:create

Sequelize [Node: 7.7.3, CLI: 2.8.0, ORM: 4.7.5]

Loaded configuration file "config/config.json".
Using environment "development".
{ Error: Cannot find module 'pg'

Edit: I see what happened here. Since you're using the pg gem here and the CLI is in my global, I had to install pg in the global as well.

[dagumak]

config.database?

[aledalgrande]

@dagumak nope, I am passing postgres because the database doesn't exist yet, so I am using the default one.