Moved to .NET standard 2.0 and dropped XUnit.NET support

After many years I could update Dynamic Specs to support .NET Standard 2.0. Thank you @Firedragonweb for your PR this changes was based on. The support for XUnit.NET was dropped in this release because it never worked really well and was actually not used by any one.

Async and type requests by attribute.

• Thanks to @Firedragonweb we support now asynchronouse tests with GivenAsnyc and WhenAsync
• We can also request types by using the RequestType attribute. In this case a default type will be injected to our SUT

Update to .Net 4.5.1

• Dynamic Specs supports now only .Net 4.5.1 and above
• Update of all external dependencies.

Back to 4.0

• .Net version is reverted to 4.0 so Dynamic Specs can be used with older versions.
• Support classes can get parameters.
• Types can be registered by support classes and extensions.

Upgrade on NUnit 3 and .Net 4.6.1

All dependencies and framework elements are upgraded to latest version thus we might have breaking changes.

v 1.3.1

• changed nuget configuration. Nothing important for production.

Version 1.3

New features:

• Dynamic Specs is now available for XUnit.net.

API Changes:

• Specifies classes do not need a Setup method any more.

Version 1.2

• When methods can use support classes.
• Specifications can be used without a generic type.