How was this not already there?

DataParser should not be required to return Any and have objects checked for type safety at runtime. This allows us to use the Swift build time type checking system with very minimal changes to existing code. The only API breaking change is that Request classes using the default JSONDataParser should now conform to JSONRequest, instead of just Request. This is because protocol extensions cannot declare default associated types.

Add QueryParameters protocol to provide interface for URL query.

Data parser associated types

While the upload is in progress, `progressHandler` closure is periodically called.
Therefore you can get information of uploading about `didSendBodyData` `totalBytesSent` `totalBytesExpectedToSend`.
These parameters are defined by `urlSession(_:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:)` in `URLSessionTaskDelegate`.

…class.

…apter` protocol.

…onTask`

Add a way to get progress of uploading.

Fix `progressHandler` to work properly

Rename Request.Parser to Request.DataParser