Always copy to the output folder just in case.

The older version of NuGet.exe was in the output folder and committed to git. This meant the file timestamps were not correct when building, and msbuild left the old file around. This will ensure we always get the results we expected.

source/OctoPack.Tasks/OctoPack.Tasks.csproj

@@ -75,14 +75,14 @@
   <ItemGroup>
     <None Include="..\tools\NuGet.exe">
       <Link>NuGet.exe</Link>
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
     <PostBuildEvent>dir
 xcopy * ..\..\..\Samples\.octopack\ /Y
-</PostBuildEvent>
+copy nuget.exe ..\..\..\Samples\.nuget\</PostBuildEvent>
   </PropertyGroup>
   <Import Project="..\packages\GitVersionTask.3.6.2\build\portable-net+sl+win+wpa+wp\GitVersionTask.targets" Condition="Exists('..\packages\GitVersionTask.3.6.2\build\portable-net+sl+win+wpa+wp\GitVersionTask.targets')" />
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">