support for auto linking urls with file protocol (#1402)

tests/Utils/MarkdownTest.php

@@ -32,6 +32,8 @@ class MarkdownTest extends TestCase
 <h1 id="test">test</h1>
 <p>asdfasdfa</p>
 <pre><code>ssdfsdf</code></pre>
+<p><a href="http://example.com/foo-bar.html" target="_blank">http://example.com/foo-bar.html</a><br />
+<a href="file:///home/kimai/images/beautiful-flower.png" target="_blank">file:///home/kimai/images/beautiful-flower.png</a></p>
 <p>sdfsdf <a href="#test-1">asdfasdf</a> asdfasdf</p>
 <h1 id="test-1">test</h1>
 <p>aasdfasdf<br />
@@ -50,6 +52,9 @@ asdfasdfa
 
     ssdfsdf
     
+http://example.com/foo-bar.html
+file:///home/kimai/images/beautiful-flower.png
+
 sdfsdf [asdfasdf](#test-1) asdfasdf
 
 # test