tmux: Align with new tmux customization for right status

These changes will align to commit
36f07a4bf19323188a0612c177d318ffe617b34e of
https://github.com/ratheesh/powerline

- Make day and week num as independent segments
- add day and week in the colorscheme for customization

Signed-off-by: Ratheesh S <ratheeshreddy@gmail.com>