- Change `Keys` type form struct to enum because we don't need to init `Keys`.

[Elonreevemusk090]

• Change Keys type form struct to enum because we don't need to init Keys.
• issue error with func get followers #79
• Do not change the .playground nor manually. -Go to/sourceand edit .swift files. -Run:generate-playground.sh`

Originally posted by @cozzin in https://github.com/ochococo/Design-Patterns-In/pull/80