Added Predis\ClientContextInterface.

This interface replaces Predis\ExecutableContextInterface and it is
used by client-side contexts such as pipelines or transactions.

src/ClientContextInterface.php

@@ -0,0 +1,48 @@
+<?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;
+
+use Predis\Command\CommandInterface;
+
+/**
+ * Interface defining a client-side context such as a pipeline or transaction.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+interface ClientContextInterface
+{
+
+    /**
+     * Sends the specified command instance to Redis.
+     *
+     * @param  CommandInterface $command Command instance.
+     * @return mixed
+     */
+    public function executeCommand(CommandInterface $command);
+
+    /**
+     * Sends the specified command with its arguments to Redis.
+     *
+     * @param  string $commandID Command ID.
+     * @param  array  $arguments Arguments for the command.
+     * @return mixed
+     */
+    public function __call($method, $arguments);
+
+    /**
+     * Starts the execution of the context.
+     *
+     * @param  mixed $callable Optional callback for execution.
+     * @return array
+     */
+    public function execute($callable = null);
+}