CSS Fix for Index Page (#69)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#69

templates/framework.html

@@ -5,7 +5,8 @@
     <title>{{ title }}</title>
     <style>
         html, body {
-            overflow-x: hidden;
+            height: 100%; /* ensure body fills viewport */
+            overflow-x: hidden; /* prevent horizontal scroll */
         }
     </style>
     {# TODO use bundles from bootstrap 3.3.7 #}