Docusign .NET Client 101

This is just the first attempt at writing some documentation for the library. It would evolve from here.

2 things you need before you can start:

1. Demo account
2. integration key

both of the above can be obtained in https://www.docusign.com/developer-center

These should be updated in the configuration section for RestSettings.Instance. and if you just want to make sure they work for unit tests - go to ConfigLoad.cs and update all the fields.