[configuration] tmux status bar configuration

I used tmux-powerline to fully pimp my tmux status bar. I was googling for a way to change to background of the status bar when your typing a tmux command. When I stumbled on this post I thought I should mention it for completeness.

Update: This project is in a maintenance mode and no future functionality is likely to be added. tmux-powerline, with all other powerline projects, is replaced by the new unifying powerline. However this project is still functional and can serve as a lightweight alternative for non-python users.