Remove Swift 5.1 warnings (#107)

Merge pull request #105 from jdisho/refactor-home-viewmodel

rename `isFirstPageLoaded` to `isFirstPageRequested`

use scan to map taps with an OrderBy state

create map(to:) operator

remove dev team

refactor HomeView and HomeVM

make the pageNumber and orderBy parameters nullable

hide the cache initializer

create isRefreshing(in:)

introduce isLoadingMore output observable

remove alertAction

make and constants and not implicitly unwrapped

simplify requestFirst and requestNext logic

simplify the filterning logic of cached photos