Tmux, default shell

Hey,

recently I've switched to Windows and trying to adapt WSL (linux subsystem) to make it play together with my habits.

This time the issue was Tmux starting bash when I need ZSH. No matter what shell was set by `chsh -s` command Tmux was don't care.

The thing I found on stackoverflow is setting `default-shell` option of Tmux to `/bin/zsh` (in my case).

Here is what you need to add to your `~/.tmux.conf`:

Don't forget to restart your Tmux or `:source-file` the new configuration.