Use GitVersion to determine package version to be produced

[CharliePoole]

Currently, we always build the version coded in the build.cake file, like 3.13.0, except on AppVeyor where we generate a unique pre-release suffix. That means the versioning of a given build is different on the local machine and any other CI servers from what it is in appveyor. By using GitVersion to determine the next version to build, we will be building the same version for a given commit on all platforms.

[CharliePoole]

This issue has been resolved in version 3.13.1

The release is available on:
GitHub.
NuGet packages are also available NuGet.org and
Chocolatey Packages may be found at Chocolatey.org