Filter out pre-releases that where released before the latest stable release (#240)

_includes/download.html

@@ -11,6 +11,11 @@
     {% elsif release_stable == nil or release.created_at > release_stable.created_at %}
     {% endif %}
 {% endfor %}
+
+{% if release_pre != nil and release_stable != nil and release_stable.created_at > release_pre.created_at %}
+        {% assign release_pre = nil %}   
+{% endif %}
+
     <section id="{{ page.section-type }}" class="content-section">
         <div class="container">
             <div class="row">