Change background randomly via app indicator

Build with

go build

On systems without the new ayatana appindicator (e.g. Fedora), use

go build -tags=legacy_appindicator

Create a configfile at ~/.config/bgchanger/config.json with content similar to the following:

{
    "pictures_dir": "/home/you/Pictures/Backgrounds",
    "interval": "15m"
}