Fancy a tech bump?

[dmalanij]

Given what's been asked #203, when opening this solution found it could use some update.

Not big deal, but at least removing the embedded nuget, including testadapters and updating nunit (similar to what was proposed in #241), upgrading other dependencies where no breaking changes (like #253), get the CI (#251), updating csproj structure, etc.

I might be working on some of those on my fork just for the sake of boredom, and if so send you a PR.