Merge pull request #5 from jovic1987/master

Added gif related constants

Author: ppavlovic

src/ContentType.php

@@ -6,4 +6,5 @@ class ContentType
 {
     const HTML = 'text/html; charset=UTF-8';
     const JSON = 'application/json; charset=UTF-8';
+    const GIF  = 'image/gif';
 }

src/Format.php

@@ -10,4 +10,5 @@ class Format
     const JSON = 'json';
     const TWIG = 'twig';
     const XML  = 'xml';
+    const GIF  = 'gif';
 }