The dotfile says that setting the major-mode leaders to nil will disable
the functionality, but there were a couple of places where that option
was not being respected.
This is how evil-leader gets `SPC m` to work for mode specific bindings,
and we need to mirror this step for `M-m`. This is big change, but in
order for `M-m` to work properly we need to remap it to the mode-map
whenever possible.
