add Newtonsoft.Json to Grpc.Core.Tests

src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj

@@ -45,6 +45,9 @@
     <Reference Include="nunitlite">
       <HintPath>..\packages\NUnitLite.3.2.0\lib\net45\nunitlite.dll</HintPath>
     </Reference>
+    <Reference Include="Newtonsoft.Json">
+      <HintPath>..\packages\Newtonsoft.Json.7.0.1\lib\net45\Newtonsoft.Json.dll</HintPath>
+    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\Grpc.Core\Version.cs">

src/csharp/Grpc.Core.Tests/packages.config

 <?xml version="1.0" encoding="utf-8"?>
 <packages>
   <package id="Ix-Async" version="1.2.5" targetFramework="net45" />
+  <package id="Newtonsoft.Json" version="7.0.1" targetFramework="net45" />
   <package id="NUnit" version="3.2.0" targetFramework="net45" />
   <package id="NUnitLite" version="3.2.0" targetFramework="net45" />
 </packages>
\ No newline at end of file