(build) use the Cake.Wyam addin as package

Author: arturcic

build/Directory.Packages.props

@@ -13,6 +13,7 @@
     <PackageVersion Include="Cake.Docker" Version="1.3.0" />
     <PackageVersion Include="Cake.Git" Version="3.0.0" />
     <PackageVersion Include="Cake.Json" Version="7.0.1" />
+    <PackageVersion Include="Cake.Wyam" Version="2.2.14" />
     <PackageVersion Include="xunit.assert" Version="2.6.6" />
   </ItemGroup>
 </Project>