Add "q" key binding for exitting the app.

[zynaxsoft]

While ZZ is indeed a nice vim-style key binding to exit the app, I find that q would be a nice addition.

The diff is simply a copy-paste of the ZZ key.

[samtay]

Good call! Would you mind also adding this to the help menu though? Right here we could just change

## Misc
**ZZ, Ctrl<c>**: Exit
**?**:           Toggle this help menu

to

## Misc
**q, ZZ, Ctrl<c>**: Exit
**?**:              Toggle this help menu

Thanks for contributing!

[zynaxsoft]

Done!