`$HOME/.tmux.conf.local` to allow for local modifications to be made
without having to modify the base code.

The `install.sh` file will create an empty `$HOME/.tmux.conf.local` file
if it doesn't already exist.

Updated the readme to include a note about putting local changes into
the appropriate file

On branch initial-changes

-  Changes to be committed:
   -	modified:   install.sh
   -	modified:   readme.md
   -	modified:   tmux/tmux.conf
   -	new file:   tmux/tmux.conf.local

creating a symlink. I don't want my develpment version being used for
production.

Had to create a copy of the following from tmux.conf to tmux.conf.local
because it was somehow getting overwritten when loading my local config

bind -r C-[ previous-window
bind -r C-] next-window
bind -r [ select-pane -t :.-
bind -r ] select-pane -t :.+
bind -r Tab last-window   # cycle thru MRU tabs
bind -r C-o swap-pane -D

On branch initial-changes

- Changes to be committed:
  -     modified:   install.sh
  -     modified:   tmux/tmux.conf.local