Update the readme.md as it was very out of date!
Remove refs to version 1.0 and version 2.0
Link to the nuget page!
Talk about semver and the upgrade from v3 to v4 and async
Take a lot of cues from https://github.com/raoulmillais/node-7digital-api/blob/master/README.md
- start with "about 7digital", "What is this code" and "you will need"
- mention and link to the api key signup microsite, about.7digital.com and developer.7digital.com
- be clear about nuget install instructions and nuget package name
Minor wording updates upon re-reading it.
Merge pull request #205 from AnthonySteele/UpdateDocs

Update the readme.md as it was very out of date!