add in-reply-to for issue comments

lib/Formats/GitHub.php

@@ -100,6 +100,10 @@ class GitHub {
       ];
     }
 
+    if($type == 'comment') {
+      $entry['in-reply-to'] = ['https://github.com/'.$org.'/'.$repo.'/issues/'.$issue];
+    }
+
     if(!empty($data['labels'])) {
       $entry['category'] = array_map(function($l){
         return $l['name'];

tests/GitHubTest.php

@@ -102,6 +102,7 @@ class GitHubTest extends PHPUnit_Framework_TestCase {
     $this->assertContains('<code class="language-php">', $data['data']['content']['html']);
     $this->assertContains('```php', $data['data']['content']['text']);
     $this->assertNotContains('name', $data['data']);
+    $this->assertContains('https://github.com/aaronpk/XRay/issues/25', $data['data']['in-reply-to']);
   }