Minor changes to Ace widget.

* Font size and family matches that of our CodeMirror editors.
* Help link to Ace keyboard shortcuts added to help.

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

@@ -135,6 +135,8 @@
                 <li><a href="http://ipython.org/ipython-doc/stable/interactive/htmlnotebook.html" target="_blank">Notebook Help</a></li>
                 <li id="keyboard_shortcuts"><a href="#">Keyboard Shortcuts</a></li>
                 <hr/>
+                <li><a href="https://github.com/ajaxorg/ace/wiki/Default-Keyboard-Shortcuts" target="_blank">Ace Keyboard Shortcuts</a></li>
+                <hr/>
                 <li><a href="http://docs.python.org" target="_blank">Python</a></li>
                 <li><a href="http://docs.scipy.org/doc/numpy/reference/" target="_blank">NumPy</a></li>
                 <li><a href="http://docs.scipy.org/doc/scipy/reference/" target="_blank">SciPy</a></li>