Add tooltip to Download/Print indicating need to save first

A real fix would be to trigger a save on each of thes actions, which would address  #852

closes gh-895

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

@@ -94,7 +94,9 b' var IPython = (function (IPython) {'
         this.content.find('#download_notebook').button();
         this.content.find('#download_notebook').attr('title',
             "Download the notebook in the specified format," +
-            " either full ipynb notebook or as a Python script.");
+            " either full ipynb notebook or as a Python script." +
+            " Make sure to save before downloading, to ensure the file is up to date."
+            );
         // upload notebook doesn't exist:
         this.content.find('#upload_notebook').button();
         this.content.find('#download_format').addClass('ui-widget ui-widget-content');

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

@@ -14,7 +14,9 b' var IPython = (function (IPython) {'
         this.element.find('button#print_notebook').attr('title',
             "Open a new window with printer-friendly HTML of the Notebook." +
             " Note that this is incomplete, and may not produce perfect" +
-            " printed output.");
+            " printed output." +
+            " Make sure to save before printing, to ensure the output is up to date."
+            );
     };
 
     PrintWidget.prototype.bind_events = function () {