Also made yarn a mandatory installation process.

Some corrections

Removed some redudant troubleshooting options

Signed-off-by: Alex Ives <alex@ives.mn>

On Arch Linux, `npm` is no longer part of the `nodejs` package; update
the list of dependencies to include `npm` instead of `nodejs.

This fixes #153.

and further review suggested by Grzegorz.

* adjustments based  on Jacob's comments

Similar to 4a5099c5

If the GPG key ever changes we would have to update it here.