Add reference to System.ValueTuple, v4.0.3.0

Author: jcansdale

src/GitHub.VisualStudio/GitHub.VisualStudio.csproj

@@ -311,6 +311,9 @@
       <HintPath>..\..\packages\Expression.Blend.Sdk.WPF.1.0.1\lib\net45\System.Windows.Interactivity.dll</HintPath>
       <Private>True</Private>
     </Reference>
+    <Reference Include="System.ValueTuple, Version=4.0.3.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\System.ValueTuple.4.5.0\lib\net461\System.ValueTuple.dll</HintPath>
+    </Reference>
     <Reference Include="System.Xml" />
     <Reference Include="PresentationCore" />
     <Reference Include="PresentationFramework" />