RestSharp UWP Does Not Build

In the master branch the UWP project does not build. Looks like the HMACSHA256 class is not available to UWP apps.

1>------ Build started: Project: RestSharp.UWP, Configuration: Debug x86 ------
1>D:\temp\wunderground\RestSharp-master\restsharp\authenticators\oauth\OAuthTools.cs(356,21,356,31): error CS0246: The type or namespace name 'HMACSHA256' could not be found (are you missing a using directive or an assembly reference?)
1>D:\temp\wunderground\RestSharp-master\restsharp\authenticators\oauth\OAuthTools.cs(356,45,356,55): error CS0246: The type or namespace name 'HMACSHA256' could not be found (are you missing a using directive or an assembly reference?)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========