This does add 81.5 mb, but I external/WixSharp weighs in at 118 mb, so I figured you wouldn't mind. If you don't like this, perhaps you can add a note to the README about installing WiX 3.10 from https://wix.codeplex.com/ (I had to figure this out myself by Googling the missing reference).
This change makes it possible to build without needing to install the WiX Toolset separately. It's actually something they recommend here:
http://wixtoolset.org/documentation/manual/v3/msbuild/daily_builds.html
This does add 81.5 mb, but I external/WixSharp weighs in at 118 mb, so I figured you wouldn't mind. If you don't like this, perhaps you can add a note to the README about installing WiX 3.10 from https://wix.codeplex.com/ (I had to figure this out myself by Googling the missing reference).