Initial commit.
Add README and example script.
Fix typo, plus rewording in README.
Properly stop PostgreSQL in the Docker commands.
Use an entrypoint for easier usage.

This adds two commands, `psql` and `run`, that can be directly called with
`docker run`. See the updated README.md file and pgserver.sh script.
Recognize when a /data volume is provided.
Use sudo instead of su.

See https://github.com/dotcloud/docker/issues/2972:

The issue describes a problem where an `scp` failing to reach the remote host
make the whole container exit. Using sudo instead of su is a possible
workaround. `scp` can be used to archive WAL segment files in the
archive_command in the PostgreSQL configuration file so we want to make sure it
can work.