Instead of binding each key in the global map, bind it in a map for the
minor mode, so they automatically disappear when the mode is turned off.
This should also prevent the key bindings from taking over in all
buffers.
The new keymap is based on some `M-' keybindings.
Instead of specifying each keybinding to enable or disable by hand, map
through a new hashtable which contains function->wrapper mappings.
