Merge pull request #193 from bwaidelich/patch-1

Add missing namespace import in `MysqlClient`

Author: clue

src/MysqlClient.php

@@ -8,6 +8,7 @@
 use React\Mysql\Io\Factory;
 use React\Promise\Deferred;
 use React\Promise\Promise;
+use React\Promise\PromiseInterface;
 use React\Socket\ConnectorInterface;
 use React\Stream\ReadableStreamInterface;