Adds fix for content-lenght value missing for files uploaded via ActionD...

...ispatch:Http::UploadedFile
@mjgiarlo So far we have only found that we need to set the Content-Length header for ActionDispatch::Http::UploadedFile objects. 

The code works without us forcing the Content-Length header for plain Strings or File objects. String and File objects have a size property but we don't need to manually set it since Faraday picks up the correct value at runtime.