made settings more testable
client testability
added TestClient base impl, added xUnit and Fluent Assertions
added test fixtures from Recurly php client, added FixtureImporter and tests
Merge branch 'testfixtures' into v2_2014_dev

Conflicts:
	Test/Recurly.Test.csproj
updated extensions with XML comments, added EnumNameToTransportConvention extension for functionality of turning .NET enum naming to the kind expected by the API, added tests