Contain files within a subdirectory

This will keep everything in one place and allow simpler maintenance in the
future.

The idea is that users will simply fork the `dotparty` repo, then add their own
custom dotfiles to it. Keeping all the core stuff in one directory will allow
for seamless updates from the upstream repository, since there shouldn't be any
collisions with user files.

The chances that the user will want to have their own `party` directory are
slim, and they can link to one on their own if they wish.
Put the README in the root

This will be necessary so visitors to the GitHub page aren't greeted with a
blank description when they get there.
Add some configuration files

One an example with all the ways it can be used, the other is the default that
`dotparty` itself will use as its base configuration in lieu/addition to the
user-provided one.