As I was creating Akka.Persistence.DocumentDb project I started looking for some CI tools available for open source projects for free. I came across this wonderful list of continuous integration services available on the internet.
Appveyor was the best suited for my application since it was .Net class library. Appveyor is free with some limitations, but if you have an open source .Net project which you want to push as a nuget package or deploy it as a website/api, it is best suited.
You could either use their web ui to setup a project or create a appveyor.yml file in your project with all the settings. Do check it out!!!!