Fix typo.
davinci-sinatra.rb not dvc-sinatra.rb
Added 208-ufo-sightings
application.css shouldn't be directly in project directory.
Added 209-world-cities
Added 210-multiple-choice
Add pry library.
Add pry.
Rebase all changes from ae2f0b5b13e7624f4394ab8272ad0af3b8bb61be to f7348a66c80959aa5f2ffe87de043d1e3385a3ba