Update Readme

2.0.4

Update Readme

Update for Swift 3 and Xcode 8

2.0.0

Remove @testable import

Handle errors for responses outside successful status codes

The request method now includes a call to .validate(), faulting to the failure block for any response outside the 200..299 range. In the request handler, we now switch on the response type, and pass through a JSON error that includes a response status code when available.