Use `TimelineCollection` to store dailies in `DailyInMemoryStore`
Use `TimelineCollection` to store dailies in `DailyInMemoryStore`

It just amazes me how little change of code I need to switch to another
type of storage.

Issue #34

NicholasTD07/SwiftDailyAPI,NicholasTD07/SwiftDailyAPI,NicholasTD07/SwiftDailyAPI