AppVeyor support

Hi Eric,

I've added minimal `appveyor.yml` to build the project and push NuGet package to artifacts along with its symbols. Removed `pause` from `build.cmd`.

To deploy NuGet packages you could either configure `NuGet` deployment in `appveyor.yml` and deploy during the build or create a new `NuGet` environment and deploy from there.

Let me know if you have any questions.