deps: qs@2.2.3
deps: update example dependencies
deps: finalhandler@0.2.0
deps: type-is@~1.5.1
deps: serve-static@~1.6.1
deps: accepts@~1.1.0
Invoke callback for sendfile when client aborts

fixes #2189
fixes #2300
closes #2303
closes #2305
Use etag to generate ETag headers
Add res.sendStatus

closes #2269
closes #2297
closes #2340