Added "edit this page" link (Codeception#162)

ThomasLandauer · DavertMik · commit 38de1c14c618 · 2019-03-19T00:09:01.000+02:00
Just a quick shot (i.e. no layout) to make editing easier. Should be included in the other "for" pages too.
diff --git a/for/symfony.md b/for/symfony.md
@@ -165,3 +165,5 @@ Actions of Symfony and Doctrine2 modules will be accessible from `$this->tester`
   <span class="glyphicon glyphicon-info-sign" aria-hidden="true"></span>
   Continue to <a href="http://codeception.com/docs/05-UnitTests">Unit Testing Guide &raquo;</a>.
 </div>
+
+[Edit this page on GitHub](https://github.com/Codeception/codeception.github.com/blob/master/for/symfony.md)
