Update UTF-8 check and move to WsServer

fixes #517

src/Ratchet/App.php

@@ -65,10 +65,6 @@ class App {
             trigger_error('XDebug extension detected. Remember to disable this if performance testing or going live!', E_USER_WARNING);
         }
 
-        if (3 !== strlen('✓')) {
-            throw new \DomainException('Bad encoding, length of unicode character ✓ should be 3. Ensure charset UTF-8 and check ini val mbstring.func_autoload');
-        }
-
         if (null === $loop) {
             $loop = LoopFactory::create();
         }

src/Ratchet/WebSocket/WsServer.php

@@ -78,6 +78,10 @@ class WsServer implements HttpServerInterface {
             throw new \UnexpectedValueException('Expected instance of \Ratchet\WebSocket\MessageComponentInterface or \Ratchet\MessageComponentInterface');
         }
 
+        if (bin2hex('✓') === 'e29c93') {
+            throw new \DomainException('Bad encoding, length of unicode character ✓ should be 3. Ensure charset UTF-8 and check ini val mbstring.func_autoload');
+        }
+
         $this->delegate    = $component;
         $this->connections = new \SplObjectStorage;