Put up release package on nuget.org

[pfeigl]

Hi Stephen,

is there a chance you can put up a version of this package as release version? We have been using Nito.AsyncEx version 4.0 for quite some time and recently updated to version 5.0. However this meant to also use this library now, as the NotifyTask got moved into this repo.

We now get build warnings while building our own release packages, because we have to reference a pre-release package.

Thanks for your great work, Philipp

[StephenCleary]

Sure, I could do that!

I'll need to disable the async commands, though, since those are not production-ready.