Adding j/k for select next/prev. Faster than up/down.

IPython/html/static/notebook/js/keyboardmanager.js

@@ -167,7 +167,6 b' var IPython = (function (IPython) {'
                 };
             }
         },
-
     }
 
     // Command mode defaults
@@ -204,6 +203,30 b' var IPython = (function (IPython) {'
                 return false;
             }
         },
+        'k' : {
+            help    : 'select previous cell',
+            handler : function (event) {
+                var index = IPython.notebook.get_selected_index();
+                if (index !== 0 && index !== null) {
+                    IPython.notebook.select_prev();
+                    var cell = IPython.notebook.get_selected_cell();
+                    cell.focus_cell();
+                };
+                return false;
+            }
+        },
+        'j' : {
+            help    : 'select next cell',
+            handler : function (event) {
+                var index = IPython.notebook.get_selected_index();
+                if (index !== (IPython.notebook.ncells()-1) && index !== null) {
+                    IPython.notebook.select_next();
+                    var cell = IPython.notebook.get_selected_cell();
+                    cell.focus_cell();
+                };
+                return false;
+            }
+        },
         'x' : {
             help    : 'cut cell',
             handler : function (event) {