Fixing a few keyboard codes and shortcuts.

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

@@ -41,7 +41,7 var IPython = (function (IPython) {
     
     // These apply to Firefox and Opera
     var _mozilla_keycodes = {
-        '; :': 59, '= +': 61, '- _': 109, 
+        '; :': 59, '= +': 61, '- _': 173, 'meta': 224
     }
     
     // This apply to Webkit and IE
@@ -176,6 +176,13 var IPython = (function (IPython) {
                 return false;
             }
         },
+        'alt+subtract' : {
+            help    : 'split cell',
+            handler : function (event) {
+                IPython.notebook.split_cell();
+                return false;
+            }
+        },
     }
 
     // Command mode defaults
@@ -426,13 +433,6 var IPython = (function (IPython) {
                 return false;
             }
         },
-        '-' : {
-            help    : 'split cell',
-            handler : function (event) {
-                IPython.notebook.split_cell();
-                return false;
-            }
-        },
         'shift+=' : {
             help    : 'merge cell below',
             handler : function (event) {