Submission for coding challenge

The file DESIGN.md contains an overview of my design and implementation choices. The code has been deployed to https://evening-meadow-8892.herokuapp.com/ on Heroku.

I also took the opportunity to fix some of the test code, for one invalid method call (*test* on a string) and for the score presence validation, that was checking for latitude and longitude.

As always, let me know if you have any questions.