The old GTK+ Hipchat on Linux had a "Quit" option that would close the app and end the process. The new Hipchat does not have a way to close it, if I close the window the process still runs in the background and there doesn't appear to be a quit menu item. I am currently running this line to close the app:

ps -A | grep HipChat.bin | cut -f 1 -d ' ' | xargs kill