Allow for discovering NVMe disks on Linux systems
Allow for discovering NVMe disks on Linux systems

This fixes an issue where `sysinfo::get_disks()` would not include any
disks with the `/dev/nvme` prefix. Rather than just checking the
`/proc/mounts` file for `/dev/sd*` disks, we now also check for
`/dev/nvme*` disks.

Closes #131.

GuillaumeGomez/sysinfo,GuillaumeGomez/sysinfo