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>
I've added a line to clean up ARGV in `Lotus::CLI`, not sure if that's exactly the place you wanted it. Maybe in `Lotus::Console` itself, since other commands probably won't have to do any ARGV cleanup? There's little chance of extracting it into any sort of convenience method