Add to readme some explanation/links about Ninject.MockingKernel

[MNF]

Could you please add to readme some explanation/links, why we should consider to use Ninject.MockingKernel.NSubstitute instead of just mocking framework.

Could you also remove dots in packages names.
The actual Nuget packages are EntityFrameworkTesting, not EntityFramework.Testing.

[scott-xu]

Using Ninject.MockingKernel.NSubstitute could save some Nsubstitute setup work. Please check the README.