Added NuGet package Microsoft.Bcl.Async for WebRequest.GetResponseAsync() & friends.
Refactor WebRequest.BeginGetResponse(...) to WebRequest.GetResponseAsync().
Removed unnecessary block causing extra indentation.
Merge pull request #4 from dlhartveld/refactor-apm-to-aa

Replacement of APM usage (Begin/EndGetResponse, etc.) with TAP (GetResponceAsync) and async/await