include current kernel name in new notebook dropdown

IPython/html/static/tree/js/newnotebook.js

@@ -67,6 +67,7 @@ define([
         if (spec) {
             display_name = spec.display_name;
             localStorage.default_kernel_name = kernel_name;
+            this.element.find("#current-kernel").text(display_name);
         } else {
             display_name = 'default kernel';
             delete localStorage.default_kernel_name;

IPython/html/templates/tree.html

@@ -49,6 +49,7 @@ data-terminals-available="{{terminals_available}}"
                     New Notebook
                   </button>
                   <button class="dropdown-toggle btn btn-default btn-xs" data-toggle="dropdown">
+                    <span id="current-kernel"></span>
                     <span class="caret"></span>
                   </button>
                   <ul id="new-notebook-menu" class="dropdown-menu"></ul>