Fix bug where direct buffer gets reclaimed.
AsyncHttpServer response hack to reset the writable callback on the socket.
AsyncNetworkSocket: null check writable callback

Change-Id: Ie0dbde9bc38694e18e595fd0bc88f6c8c6e9e2a7
Ion: Fix issue 74.
https://github.com/koush/ion/issues/74

When serving a cached or conditional cached response, the byte buffer
must be properly limited to the content length.

Change-Id: I0948c13d1bb9060f409c70b59351915c98ed3dc1
v1.1.9

Change-Id: I010d61b63f91bfeef222d515af93080229a8b5e2