Use decoded_content in response logging, because gzip is unreadable for mere humans

Hi Ivan,

I ran into trouble trying to access a soap service, and couldn't really figure out how to debug at first. The response logging looked like gibberish. So I looked at how you do the debugging through WWW::Mechanize, and that module's response_done handler doesn't automatically decode gzip'ed data. I had similar difficulty passing in a log object. So I tried patching the W3C::SOAP::Client module, changed "content" to "decoded_content" in a couple of places, and there was the actual response body, logged through my own logging object! That will make debugging a lot easier in the future.

Thanks for a great set of modules! 
Rhesa