Force tabs to space in CM

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

@@ -41,6 +41,7 b' var IPython = (function (IPython) {'
             mode: 'python',
             theme: 'ipython',
             readOnly: this.read_only,
+            extraKeys: {"Tab": "indentMore","Shift-Tab" : "indentLess"},
             onKeyEvent: $.proxy(this.handle_codemirror_keyevent,this)
         });
         input.append(input_area);

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

@@ -35,6 +35,7 b' var IPython = (function (IPython) {'
             value: this.placeholder,
             readOnly: this.read_only,
             lineWrapping : true,
+            extraKeys: {"Tab": "indentMore","Shift-Tab" : "indentLess"},
             onKeyEvent: $.proxy(this.handle_codemirror_keyevent,this)
         });
         // The tabindex=-1 makes this div focusable.