Remove iptables copypasta

Was outside a heredoc, probably inadvertently.
Enable kernel ipv4 forwarding

So the iptables rules actually work.
Replace udhcpd with dnsmasq for DHCP/DNS
Change wordpress/nginx host to `vspi`

So dnsmasq will be able to resolve browser requests to http://vspi/.

Note that `vspi.local` will still resolve for any computers using mDNS,
which is everything except windows XP/7. These requests should
be redirected to `vspi` after the first page however.
Document software architecture in more detail

Also update link to `vspi` domain.
Merge pull request #3 from blendmaster/dnsmasq

Improves reliability of DNS and allows for local .vspi top-level domain.