Connect Ruby app to database.

  - Install MySQL2 gem
  - Connect Sinatra app to database
Of course this can be done, for now I kept the logic simple. The connection is checked at container level in the bash script, and the the app level through this check. It will throw and error if the app wasn't connected to the database.
We can build a more complex user story for the next sprint and write a new blog post and a demo with a Rails app for example,and we can add models etc.