My part 1 solution

Sorry, I don't know how to limit this PR to only some files. Feel free to disregard the answers file. 

However, I would love to get a little feedback on `RubyLs::Application`. As always when writing code like this, I'm unsure of what to put in instance vars and what to pass around as method arguments. I'm not 100% happy with the way the code is factored, but I'm also not sure how to improve it. Maybe by extracting some concerns into separate classes? 

I also rewrote the the test runner to output lots of info if a test fails. This was very useful during development.