0.9.4-beta

Moved Sync-over-Async versions of TableContext operations into namespace FSharp.AWS.DynamoDB.Scripting
Added WithMetricsCollector() copy method to allow separating metrics by context (eg by request)
Ensured metrics are reported even for failed requests
Added TryGetItemAsync (same as GetItemAsync, but returns None, instead of throwing, if an item is not present)
Switched test framework to Xunit, assertions to Unquote, runner to dotnet test