Rename command classes using command ID as name.

Some notable exceptions are EVAL and ECHO because having these names
as class names would raise a syntax error.

src/Command/Redis/SUBSTR.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Predis package.
+ *
+ * (c) Daniele Alessandri <suppakilla@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Predis\Command\Redis;
+
+use Predis\Command\Command as RedisCommand;
+
+/**
+ * @link http://redis.io/commands/substr
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class SUBSTR extends RedisCommand
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getId()
+    {
+        return 'SUBSTR';
+    }
+}