httphi router refactor (#176)

* httphi: RouterConfig refactor to enable DefaultRouterConfig

* RequestHeader not case sensitive anymore

* httphi: use DefaultRouterConfig in examples

* httphi: remove gated stage complexity

Misusing Stage methods by calling them once header has been written is totally harmless as far as I can tell. We simplify the codebase on this occasion by removing the headerWritten check for all stage methods

* httphi: improve APIs

* httphi: remove status

http/httphi/status.go

@@ -3,7 +3,7 @@ package httphi
 // StatusText returns a text for the HTTP status code. It returns the empty
 // string if the code is unknown.
 func StatusText(code int) string {
-	switch status(code) {
+	switch code {
 	case StatusContinue:
 		return "Continue"
 	case StatusSwitchingProtocols:
@@ -133,10 +133,6 @@ func StatusText(code int) string {
 	}
 }
 
-const ()
-
-type status int
-
 // HTTP status codes as registered with IANA.
 // See: https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
 const (