Upgrade to support Preview 8

This release makes the library preview 8 compatible. It also changes the target framework to netstandard2.0 for a wider target audience.

Download from nuget: https://www.nuget.org/packages/Razor.Components.Testing.Library/0.1.0-preview8-19405-7-1

Initial release

First release with a nuget package published to nuget.org:

https://www.nuget.org/packages/Razor.Components.Testing.Library