Revert to NuGet 3.3 to fix broken build

Author: daviwil

appveyor.yml

@@ -30,6 +30,7 @@ install:
 - git submodule -q update --init
 
 before_build:
+- ps: if (Test-Path 'C:\Tools\NuGet3') { $nugetDir = 'C:\Tools\NuGet3' } else { $nugetDir = 'C:\Tools\NuGet' }; (New-Object Net.WebClient).DownloadFile('https://dist.nuget.org/win-x86-commandline/v3.3.0/nuget.exe', "$nugetDir\NuGet.exe")
 - nuget restore
 
 build: