TrackerDog 2.2.1: Bugfix release and merging v2-net-standard on v2 branch

v2-net-standard branch has been definitively meged with v2 branch, hence, the last becomes the official and maintained branch again.

Also, Visual Studio project has been migrated to Visual Studio 2017.

This release is a bugfix to #29 issue.

v2.2.1 unsigned and signed NuGet packages have been already pushed to NuGet Gallery!

Finally, official docs have been updated to reflect the latest changes. Check it now on http://matiasfidemraizer.com/trackerdog