Update NoWarn as per https://github.com/dotnet/sdk/issues/1205#issuecomment-302579464

Ix.NET/Source/Directory.build.props

@@ -12,7 +12,7 @@
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>    
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)ReactiveX.snk</AssemblyOriginatorKeyFile>
-    <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <NoWarn>$(NoWarn);1701;1702;CS1591</NoWarn>
     <DefaultLanguage>en-US</DefaultLanguage>
     <IncludeSymbols>false</IncludeSymbols>
     <IsTestProject>$(MSBuildProjectName.Contains('Test'))</IsTestProject>

Ix.NET/Source/Tests/Tests.csproj

@@ -17,7 +17,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0-preview-20170601-03" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.0-beta3-build3705" />
     <PackageReference Include="xunit" Version="2.3.0-beta3-build3705" />
     <PackageReference Include="FluentAssertions" Version="4.19.2 " />