consistently get the first cell

IPython/html/tests/casperjs/test_cases/execute_code_cell.js

@@ -3,7 +3,7 b''
 //
 casper.notebookTest(function () {
     this.evaluate(function () {
-        var cell = IPython.notebook.get_selected_cell();
+        var cell = IPython.notebook.get_cell(0);
         cell.set_text('a=10; print a');
         cell.execute();
     });