Match the max tooltip and bottom area sizes in the notebook.

This prevents the tooltip from going below the bottom of the page,
which makes it inaccessible by any mechanism and thus useless.

IPython/frontend/html/notebook/static/css/notebook.css

@@ -372,7 +372,7 @@ div.text_cell_render {
 
 /*properties of tooltip after "expand"*/
 .bigtooltip{
-    height:60%;
+    height:30%;
 }
 
 /*properties of tooltip before "expand"*/

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

@@ -44,7 +44,7 @@ var IPython = (function (IPython) {
         // ii) to prevent the div from scrolling up when the last cell is being
         // edited, but is too low on the page, which browsers will do automatically.
         var that = this;
-        var end_space = $('<div class="end_space"></div>').height(150);
+        var end_space = $('<div class="end_space"></div>').height("30%");
         end_space.dblclick(function (e) {
             if (that.read_only) return;
             var ncells = that.ncells();