add instructions to install on debian/ubuntu

Fix 0 package count in Slackware

Fixes #112.

Rationale:
- By default in Slackware, /sbin and /usr/sbin aren't part of the user's
  PATH. (It's been this way since I started using it in 2004, version
  9.1)
- `type -p /path/to/binary` works just like it was used with a bare
  binary name.

Rename fetch to neofetch

Don't create a config file in stdout mode.

Battery: Added support for NetBSD

Fix the battery check on PCs without a battery.

Added function to display currently logged in users

New Readme Picture