Add Link to Walkthrough (Do not merge yet)

For a more detailed step-by-step walkthrough to setting up a development environment, setting up, and using the project, please see the following: github.com/richardkiss/pycoin/blob/master/STEP-BY-STEP.md

I want to produce a more detailed walkthrough for newbie programmers to learn how to build and use a Bitcoin program with this.

Please merge once I have the STEP-BY-STEP.md file touched.