Add the tools feed back to NuGet.config

NuGet.config

@@ -3,6 +3,7 @@
   <packageSources>
     <clear />
     <add key="AspNetCore" value="https://dotnet.myget.org/F/aspnetcore-master/api/v3/index.json" />
+    <add key="AspNetCoreTools" value="https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json" />
     <add key="AspNetCorePatch" value="https://dotnet.myget.org/F/aspnet-1-0-6-september2017-patch/api/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>