As indicated by the BufferedInputStream-Implementation, an InputStream may read just the available bytes.
Thus it is an error to expect a single unchecked read to return the full response.
async callback may now be called after the future completes
+AsyncClientHttpEngine: Optional ClientHttpEngine-Extension for async httpclients
Support AsyncClientHttpEngine. Also changes behaviour of submit(InvocationCallback) to call the callback
seemingly after the future-object is signaled completion.
prepare for ApacheHttpAsyncClient4Engine
Apache HttpAsyncClient as optional dependency
fix possible NPE
...and some unrelated nitpicks