When index == lastIndex we still want to send the value.

Otherwise we won’t send the replayed when lastIndex = 0 and only one
value has been sent.
Add a HotSignalSpec to test replay.
Link LlamaKit.
Start with an initial state of -1.
Revert "When index == lastIndex we still want to send the value."

This reverts commit 3a764e4e2eb48026ac032707ea8a310b1d0bdb59.
Rename some of the test vars.
new line.
Add some tests for replay(2).

That *should* mean it works for any n ;) (by sorta hand wavy induction…
:trollface:).
Remove this logging.
Add some tests for replay(0)
Swift style.
context -> describe.
Use the TestScheduler.
Use a better dummy error.
Project should use tabs.
collect the values and send 2 for the replay(0) test.
Test that forwarding continues.
Style.
Whoops. didSet gets the oldValue.
Test replay(2) continues forwarding.