get rid of resize boxes in IE11

Author: jhchen

assets/base.styl

@@ -78,7 +78,9 @@ iconPadding = 3px inputPadding
     margin-bottom: 5px
     margin-top: 5px
     padding-left: 16px
-  code, pre:not(.hljs)    // TODO core should not be aware of hljs
+  pre.hljs
+    overflow: visible
+  code, pre:not(.hljs)
     background-color: #f0f0f0
   code, pre
     border-radius: 3px