Swift 5 Support (Alba is deprecated)

0.7.0

update for Swift 5

0.4.0: Don’t call it «unsafe». Call it manual.

This update is a breaking one — it renames UnsafeSubscribe type (and unsafe property on Subscribe) to ManualSubscribe (and manual). Using the term «unsafe» was misleading because in Swift the term «unsafe» means «can corrupt memory», and there was nothing like that in Alba. So now it’s renamed to «manual» expressing that you should manually unsubscribe if you use it.

It also, of course, incorporates changes from the latest 0.3.x releases — such as flatSubscribe method and FlatWeakSubscribe proxy (accessible via .weak(_:).flat)