Updated NuGet
Updated to RxUI 5.1.2.  Updated Microsoft.Bcl.Async to 1.0.16
Updated Microsoft BCL Build Components for SL project

Removed useless BCL packages for WinRT test project
Updated ReactiveUI from v4.6.4 to v4.6.5 for SL project
Updated ReactiveUI to v5.2.0
Updated nuspec file