Don't set Content-Type to application/json in query without body

internal/client/route_list.go

@@ -9,5 +9,5 @@ import (
 // ListRoutes list the routes registered on the kapow! instance
 func ListRoutes(host string, w io.Writer) error {
 	url := host + "/routes/"
-	return http.Get(url, "application/json", nil, w)
+	return http.Get(url, "", nil, w)
 }