Add simple gravatar hash twig filter

src/Packagist/WebBundle/Resources/views/layout.html.twig

@@ -50,7 +50,7 @@
                         {%- if app.user %}
                             <li class="nav-user">
                                 <section>
-                                    <img width="57" height="57" alt="" src="https://secure.gravatar.com/avatar/b494363ed38b483b240180920c0d38c2?d=https://a248.e.akamai.net/assets.github.com%2Fimages%2Fgravatars%2Fgravatar-user-420.png">
+                                    <img width="57" height="57" alt="" src="http://www.gravatar.com/avatar/{{ app.user.email|gravatar_hash }}">
                                     <a href="{{ path('fos_user_profile_show') }}">{{ app.user.username }}</a>
 
                                     <section class="nav-user-menu">

src/Packagist/WebBundle/Twig/PackagistExtension.php

@@ -28,7 +28,8 @@ class PackagistExtension extends \Twig_Extension
     public function getFilters()
     {
         return array(
-            'prettify_source_reference' => new \Twig_Filter_Method($this, 'prettifySourceReference')
+            'prettify_source_reference' => new \Twig_Filter_Method($this, 'prettifySourceReference'),
+            'gravatar_hash' => new \Twig_Filter_Method($this, 'generateGravatarHash')
         );
     }
 
@@ -68,4 +69,9 @@ class PackagistExtension extends \Twig_Extension
 
         return $sourceReference;
     }
+
+    public function generateGravatarHash($email)
+    {
+        return md5(strtolower($email));
+    }
 }