Add support for pacman

[lll2yu]

Please consider adding support for pacman(Arch Linux package manager).

[himanshub16]

I am an Arch user now, and this is how I've been using here.

• Set your sudo config to use http_proxy and https_proxy from the user running the sudo command.
  OR
• Use sudo -E for sudo. This preserves environment variables for sudo command used.

For references, refer https://stackoverflow.com/questions/8633461/how-to-keep-environment-variables-when-using-sudo