Add a rotate filter (fix #15)

tests/FFMpeg/Tests/Filters/Video/RotateFilterTest.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace FFMpeg\Tests\Filters\Video;
+
+use FFMpeg\Filters\Video\RotateFilter;
+use FFMpeg\Tests\TestCase;
+
+class RotateFilterTest extends TestCase
+{
+    public function testApply()
+    {
+        $video = $this->getVideoMock();
+        $format = $this->getMock('FFMpeg\Format\VideoInterface');
+
+        $filter = new RotateFilter(RotateFilter::ROTATE_90);
+        $this->assertEquals(array('-vf', RotateFilter::ROTATE_90, '-metadata:s:v:0', 'rotate=0'), $filter->apply($video, $format));
+    }
+
+    /**
+     * @expectedException \FFMpeg\Exception\InvalidArgumentException
+     * @expectedExceptionMessage Invalid angle value.
+     */
+    public function testApplyInvalidAngle()
+    {
+        new RotateFilter('90');
+    }
+}