Update CHANGELOG.md

Author: clue

CHANGELOG.md

@@ -8,16 +8,16 @@
   (#38 by @clue)
 
   ```php
-// old
-$client->on('data', function (MessageInterface $message, Client $client) {
-    // process an incoming message (raw message object)
-});
-
-// new
-$client->on('data', function (MessageInterface $message) use ($client) {
-    // process an incoming message (raw message object)
-});
-```
+  // old
+  $client->on('data', function (MessageInterface $message, Client $client) {
+      // process an incoming message (raw message object)
+  });
+
+  // new
+  $client->on('data', function (MessageInterface $message) use ($client) {
+      // process an incoming message (raw message object)
+  });
+  ```
 
 > Contains no other changes, so it's actually fully compatible with the v0.5.2 release.