Concatenation feature (#287)

* Creation of a feature to concatenate files into a new one.

* Update of the README
* Creation of the tests for the concatenation
* We use an array of videos instead of a path to a text files
* We use the bundle Temporary File System instead of getcwd

src/FFMpeg/Filters/Concat/ConcatFilterInterface.php

@@ -0,0 +1,20 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Strime <contact@strime.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Filters\Concat;
+
+use FFMpeg\Filters\FilterInterface;
+use FFMpeg\Media\Concat;
+
+interface ConcatFilterInterface extends FilterInterface
+{
+    public function apply(Concat $concat);
+}

src/FFMpeg/Filters/Concat/ConcatFilters.php

@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Strime <contact@strime.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Filters\Concat;
+
+use FFMpeg\Media\Concat;
+
+class ConcatFilters
+{
+    private $concat;
+
+    public function __construct(Concat $concat)
+    {
+        $this->concat = $concat;
+    }
+}