appveyor restore github release 

update appveyor, remove github deployment for now, bump version to 2.9.1 

update appveyor, remove github deployment for now, bump version to 2.9.1 

Merge branch 'develop' 

Merge branch 'rmunn-feature/getopt-mode' into develop 

prepare for release 2.9 

Publish Release 2.8.0 

regenerate nuget key and reencrypt 

Update readme.md 

Add Linux as CI in appveyor (#598)