Update celltoolbar.js

I want to write an extension with multiple select bar. They are supposed to be displayed inline, not in block mode. The better way is to use span instead of div.

IPython/html/static/notebook/js/celltoolbar.js

@@ -342,7 +342,7 @@ define([
                         setter(cell, !v);
                         chkb.attr("checked", !v);
             });
-            button_container.append($('<div/>').append(lbl));
+            button_container.append($('<span/>').append(lbl));
         };
     };
 
@@ -406,7 +406,7 @@ define([
             select.change(function(){
                         setter(cell, select.val());
                     });
-            button_container.append($('<div/>').append(lbl).append(select));
+            button_container.append($('<span/>').append(lbl).append(select));
         };
     };