Setting a baseline config with a dummy database

- For spec_helper, when files are required, there's no config yet
  and Sequel::Model requires on
- I have to set-up a database connection, and without the config, that would
  die
- I altered Pomodori::Config#read_config to set a database-only config if
  no config file is where we expect to find one
- TODO: Use "needs_setup" to set a message outside of RSpec