Work around a IE10 bug.

IE 10 doesn't appear to properly handle calc(100% - 26px), breaking scrolling
of contacts.

css/converse.css

@@ -717,11 +717,10 @@
       cursor: pointer; }
     #conversejs #converse-roster .roster-contacts {
       margin: 0;
-      max-height: 195px;
-      max-height: calc(100% - 26px);
+      max-height: 100%;
       overflow-x: hidden;
       overflow-y: auto;
-      padding-bottom: 15px; }
+      padding-bottom: 41px; }
     #conversejs #converse-roster .group-toggle {
       color: #6C4C44;
       display: block;

sass/_core.scss

@@ -769,11 +769,10 @@
     }
     .roster-contacts {
       margin: 0;
-      max-height: 195px;
-      max-height: calc(100% - 26px);
+      max-height: 100%;
       overflow-x: hidden;
       overflow-y: auto;
-      padding-bottom: 15px;
+      padding-bottom: 41px;
     }
     .group-toggle {
       color: $text-color;