Add fixed html and body height, avoid scrollbar

mythril/analysis/templates/callgraph.html

@@ -15,6 +15,9 @@
             color: #ffffff;
             font-size: 10px;
         }
+        html, body {
+          height: 95%;
+        }
     </style>
     {% else %}
     <style type="text/css">
@@ -27,6 +30,9 @@
             font-size: 10px;
             font-family: "courier new";
         }
+        html, body {
+          height: 95%;
+        }
     </style>
     {% endif %}