[gentoo-doc] Some Updates to the Quick Install Guide

[Daniel Meltzer]

Hello Everyone.

I recently reinstalled gentoo after a long hiatus, and noticed that a
lot of documentation has aged a bit over time and grown out of sync.
Being that I dislike this, I'm setting out to try and clean some of it
up.  My first project was updating the quickinstall guide to reflect
some of the changes that have been made to the handbook over the last
few years.  I doubt I have covered all of them, but I think this takes
care of the glaring differences.  I'm going to send these along via
the fancy git commands this time.  If you want me to make them go to
bugzilla in the future I'll be happy to do that, this just seemed like
a more approachable first step. 

I think it would make sense to turn this into a x86/amd64 combined
guide as well, I haven't started on that yet but with the prevelance
of 64bit systems these days the x86 is kind of falling by the wayside.
Please take a look at these patches, and let me know what you think.
I will send more as time permits.

Thanks,

Dan.