Spec boilerplate

@angusbayley In response to your email

If you run `bundle exec rspec spec` in the project root, you should be able to get up and running quite quickly.

I've set up a framework of sorts which you can work with, some methods and specs are yet to be written - to be solved by the reader!

Essentially, the sinatra `app.rb` file now just calls a few well defined services. The app itself isn't tested (this can be done later) but the services each have simple spec files.