Enhancement to the OOTB behaviour for AutoFixture.NUnit2

Manually adding binding redirect for `nunit.core.interfaces.dll` fixes the issue with Resharper 8.1 and greater this resolves #246

Included `nunit.core.interfaces.dll` similar to [NUnitTestAdapter](http://www.nuget.org/packages/NUnitTestAdapter/) this fixes the OOTB and resolves #275