Sports, Leagues, and Bears! Oh my.

:construction: **In Progress** :construction: 

This PR will cover the creation of Sports and Leagues. Leagues can only belong to a single sport. You'll have to select a Sport when creating a League. :sparkles: 

Everything has tests to to protect yourself @briannelsondesign. :grinning: I'll show you how to run them so you can keep things not-broken. You will learn Rails, young padawan. :tea: 

- [x] Be able to create, edit, and destroy a Sport via the UI
- [x] Be able to create, edit, and destroy a League belonging to a sport via the UI
- [x] Add `controller` tests (and maybe an integration test or two)