Hide the slide number in the title outside of present mode

www/slide/slide.less

@@ -138,6 +138,7 @@ body {
         page-break-after: always;
         position: relative;
         box-sizing: border-box;
+        overflow: hidden;
         li {
             min-width: @ratio*50vw;
         }
@@ -210,6 +211,7 @@ div.modal, div#modal {
         overflow: visible;
         white-space: nowrap;
         .slide-frame {
+            overflow: hidden;
             display: inline-block;
             box-sizing: border-box;
             border: 1px solid;