Improve the readme
Improve the readme

Mostly rewording and reordering, based on https://github.com/gregjd/opendatadc/commit/2bd1565a9b8fd7188c8382915e37a56efbcd1a43
codefordc/opendatadc,codefordc/opendatadc,codefordc/opendatadc,codefordc/opendatadc