Add a simple `lotus console` command

`lotus console` will spawn an IRB (or Pry, if bundled) session that
loads the application code. This is a very basic analogue to `rails
console` and would be nice for testing out code ideas or modifying the
database.

Signed-off-by: David Celis <me@davidcel.is>
My first thought would be to introduce `fakefs` and simply write a `pry.rb` file that defines the Pry constant with a dummy `start` method. But perhaps that's overkill and there's a better way. It would, however, prevent me from having to muck with the existing test fixtures. I could write a dummy `config/applications.rb` file the same way and the library would be useful for other tests that require files to be present only in certain contexts.