Use ~/.config/aur as default folder

[jgsqware]

In linux, ~/.config is more a default than ~ to store app-data.

This pull request propose ~/.config/aur as default

[pigmonkey]

I agree home isn't the best place. I don't think ~/.config is appropriate either. XDG_CACHE_HOME seems like the best place.

Do you want to make a PR that checks if $XDG_CACHE_HOME is set in the environment and if not falls back to ~/.cache?