The existing distribution detection does not work on Arch Linux
without the `lsb-release` package installed. This patch adds
detection using `/etc/os-release` in the same way that f9a1881
uses for Fedora and CentOS detection.
I changed the if statement that Bryn Sinclair used to a case
statement to avoid extra if-else-if statements.
I also needed to add a trim statement to remove the `"` characters
that are present in Arch Linux's `/etc/os-release` file.