Fix case where command namespace contains Command

Fixes the case where a command has a namespace that contains the string
'Command'. For example: Acme/Commanding/LaunchMissileCommand where
only the last instance of 'Command' should be replaced with 'CommandHandler'
and 'Validator'.

src/Laracasts/Commander/BasicCommandTranslator.php

@@ -11,7 +11,8 @@ class BasicCommandTranslator implements CommandTranslator {
      */
     public function toCommandHandler($command)
     {
-        $handler = str_replace('Command', 'CommandHandler', get_class($command));
+        $commandClass = get_class($command);
+        $handler = substr_replace($commandClass, 'CommandHandler', strrpos($commandClass, 'Command'));
 
         if ( ! class_exists($handler))
         {
@@ -31,7 +32,8 @@ public function toCommandHandler($command)
      */
     public function toValidator($command)
     {
-        return str_replace('Command', 'Validator', get_class($command));
+        $commandClass = get_class($command);
+        return substr_replace($commandClass, 'Validator', strrpos($commandClass, 'Command'));
     }
 
 }