Truncating response body

[JimTools]

truncating the body to reduce data transmission on cache hits.

closes #54

[odan]

I've been thinking about this approach. Wouldn't it be easier to implement a custom middleware that checks the response for status code 304 and, if the case, returns a response with an empty body. The advantage would be that this can be added when needed and doesn't break the existing logic.

[flavioheleno]

Honestly, dropping the body is something that I'd expect from this middleware and not have to add another one to handle it. IMHO, the current behavior/logic is broken.

[akrabat]

I've updated to make the StreamFactory optional which keeps BC with current implementations. Also merged in the latest 1.x branch.