underline keyboard shortcut letter on buttons

IPython/frontend/html/notebook/static/js/savewidget.js

@@ -112,7 +112,7 b' var IPython = (function (IPython) {'
 
 
     SaveWidget.prototype.status_save = function () {
-        this.element.find('button#save_notebook').button('option', 'label', 'Save');
+        this.element.find('button#save_notebook').button('option', 'label', '<u>S</u>ave');
         this.element.find('button#save_notebook').button('enable');
         IPython.print_widget.enable();
     };

IPython/frontend/html/notebook/templates/notebook.html

@@ -42,7 +42,7 b''
     <span id="save_widget">
         <input type="text" id="notebook_name" size="20"></textarea>
         <span id="notebook_id" style="display:none">{{notebook_id}}</span>
-        <button id="save_notebook">Save</button>
+        <button id="save_notebook"><u>S</u>ave</button>
     </span>
     <span id="kernel_status">Idle</span>
 </div>
@@ -87,29 +87,29 b''
             <div class="section_content">
                 <div class="section_row">
                     <span class="section_row_buttons">
-                        <button id="delete_cell">Delete</button>
+                        <button id="delete_cell"><u>D</u>elete</button>
                     </span>
                     <span class="section_row_header">Actions</span>
                 </div>
                 <div class="section_row">
                     <span id="cell_type" class="section_row_buttons">
-                        <button id="to_code">Code</button>
+                        <button id="to_code"><u>C</u>ode</button>
 <!--                        <button id="to_html">HTML</button>-->
-                        <button id="to_markdown">Markdown</button>
+                        <button id="to_markdown"><u>M</u>arkdown</button>
                     </span>
                      <span class="button_label">Format</span> 
                 </div>
                 <div class="section_row">
                     <span id="cell_output" class="section_row_buttons">
-                        <button id="toggle_output">Toggle</button>
+                        <button id="toggle_output"><u>T</u>oggle</button>
                         <button id="clear_all_output">ClearAll</button>
                     </span>
                     <span class="button_label">Output</span>
                 </div>
                 <div class="section_row">
                     <span id="insert" class="section_row_buttons">
-                        <button id="insert_cell_above">Above</button>
-                        <button id="insert_cell_below">Below</button>
+                        <button id="insert_cell_above"><u>A</u>bove</button>
+                        <button id="insert_cell_below"><u>B</u>elow</button>
                     </span>
                     <span class="button_label">Insert</span>
                 </div>