Adjust README to remove redundancy and differences with Development Guide

[wright-io]

README.md has some details in the "Development" section which are redundant with, and sometimes different from the guidance in the Development Guide (docs/development.md). The README currently points to the Development Guide.

The proposed approach would be:

• Retain the link to the developer reference guides in the README
• Remove the detailed development information from the README (moving anything unique and useful into the development guide if it isn't already there).