Add logger macro to easily setup custom log_handler

src/kemal/base_log_handler.cr

@@ -6,6 +6,7 @@ class Kemal::BaseLogHandler < HTTP::Handler
   end
 
   def call(context)
+    call_next context
   end
 
   def write(message)

src/kemal/config.cr

@@ -19,7 +19,6 @@ module Kemal
 
     def logger=(logger : Kemal::BaseLogHandler)
       @logger = logger
-      HANDLERS << @logger.not_nil!
     end
 
     def scheme

src/kemal/macros.cr

@@ -34,10 +34,17 @@ end
 # development: STDOUT in
 # production: kemal.log
 macro log(message)
-  Kemal::LogHandler::INSTANCE.write "#{{{message}}}\n" if Kemal.config.logging
+  Kemal.config.logger.write "#{{{message}}}\n"
 end
 
 # Enables / Disables logging
 macro logging(status)
   Kemal.config.logging = {{status}}
+end 
+
+macro logger(logger) 
+  Kemal.config.logger = {{logger}}
+  Kemal.config.add_handler {{logger}}
 end
+
+