Use Newtonsoft.Json 9.0.1.

As this is the latest version supported for VS2017 extensions.

Author: grokys

src/GitHub.Api/GitHub.Api.csproj

@@ -27,7 +27,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="2.6.1" />
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
     <PackageReference Include="Octokit.GraphQL" Version="0.1.1-beta" />
   </ItemGroup>
 </Project>

src/GitHub.App/GitHub.App.csproj

@@ -46,7 +46,7 @@
     <PackageReference Include="Microsoft.VisualStudio.Editor" Version="14.3.25407" />
     <PackageReference Include="Microsoft.VisualStudio.SDK.EmbedInteropTypes" Version="15.0.17" />
     <PackageReference Include="Microsoft.VisualStudio.Shell.14.0" Version="14.3.25407" />
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
     <PackageReference Include="Octokit.GraphQL" Version="0.1.1-beta" />
     <PackageReference Include="Rothko" Version="0.0.3-ghfvs" />
     <PackageReference Include="Serilog" Version="2.5.0" />