Update README to show hierarchical names

[notCalle]

Pallets can be structured in inheritance hierarchies, for grouping
and/or name space separation. Examplify this in the documentation.

Fixes #96.

[creideiki]

The file tree in README.md shows the example warehouse, so you can't have dns-resolver/example-net/ without actually adding it. Then again, the current naming convention is crap, because dhcp-server-example-net/ is supposed to refer to "the example network", whereas dns-resolver/example-com/ is supposed to refer to "the domain example.com".

I think it would be best if you just drop the lines with dns-resolver/example-net/ in this pull request, and then I'll change the DHCP service configuration separately. Or, if you want, you can fix the DHCP service configuration here as well.

[notCalle]

Repushed with amendment.