Server-side Chunked Transfer Encoding

hi @daedric,

This pull-request adds chunked Transfer Encoding on the server side only. It currently doesn't allow sending of additional headers during the response, as I didn't think that would be an immediate use-case opposed to streaming just the content.

I've also removed the minor_, and major_ version members from the Response class as they were not being exposed/used in client code. I can't think of a client that would require HTTP 1.0 these days, but it would be easy to add back in if required.

Cheers
Matt


The implicit conversion to bool doesn't work as I'd hope in this case, e.g. with "return chunkedBodyCallback_;"  using  G++ 4.8 I get  error: no viable conversion from 'const std::function<std::string ()>' to  'bool'

I'll change this to "chunkedBodyCallback_ != nullptr" instead of zero.