Merge pull request #4022 from ivanov/doc-links

DOC: fix links to matplotlib, notebook docs

IPython/html/templates/notebook.html

@@ -156,14 +156,15 @@ class="notebook_app"
         <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Help</a>
             <ul class="dropdown-menu">
                 <li><a href="http://ipython.org/documentation.html" target="_blank">IPython Help</a></li>
-                <li><a href="http://ipython.org/ipython-doc/stable/interactive/htmlnotebook.html" target="_blank">Notebook Help</a></li>
+                <li><a href="http://ipython.org/ipython-doc/stable/interactive/notebook.html" target="_blank">Notebook Help</a></li>
                 <li id="keyboard_shortcuts"><a href="#">Keyboard Shortcuts</a></li>
                 <li class="divider"></li>
                 <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>
+                <li><a href="http://matplotlib.org/" target="_blank">Matplotlib</a></li>
                 <li><a href="http://docs.sympy.org/dev/index.html" target="_blank">SymPy</a></li>
-                <li><a href="http://matplotlib.sourceforge.net/" target="_blank">Matplotlib</a></li>
+                <li><a href="http://pandas.pydata.org/pandas-docs/stable/" target="_blank">pandas</a></li>
             </ul>
         </li>
     </ul>