* refactor RedirectHandler
- `redirectState` is no longer a property of `HTTPClient.Request`. RedirectHandler now stores this state directly and therefore no longer optional.
- we no longer count the number of allowed redirects down. Instead the number of redirects is dervied from `self.visited.count` and we compare it to the maxRedirect to check if we git the limit.
* `HTTPClient.Configuration.RedirectConfiguration.Configuration` is now called `HTTPClient.Configuration.RedirectConfiguration.Mode`
only two `Configuration`s left in the type name
* add redirect logger test
