Fixing Tmux key binding conflict.

Switching between panes using Vim-like bindings wasn't working for 'k'
as this was also bound to 'kill'.
Removing Tmux key bindings for zooming panes.

Tmux 1.8 has built in zoom malarkey going on so remove these settings as
they do not work in Spectrwm anyway.  Spectrwm uses these for switching
workspaces.