[Markdig.Wpf] Update assembly info and nuget manifest.

[Markdig.Wpf] Bump to version 0.2.3

[Markdig.Wpf] Bump to version 0.2.2

[Nuget] Update nuspec for version 0.2.1.

[Markdig.Wpf] Bump to version 0.2.0

[Markdig.Xaml] Bump to version 0.1.3

[Markdig.Xaml] Bump to version 0.1.2

[Markdig.Xaml] Bump to version 0.1.1

First release.

Currently only Markdig.Xaml is working. See Markdig.Xaml.ConsoleApp and Markdig.Xaml.SampleApp for examples on how to use it.