add agent/keepalive tests
flush headers if expect sent, per node.js documentation
shore up and clarify socket error/close event handling, fixes issue where DNS lookup failure could cause exception due to unhandled error event
workaround lack of tcp-close (https://github.com/tessel/runtime/issues/336) to let server-errors test finish; also add note about other weird slowness
fix bug where headers not gathered properly after 100 Continue response
fix up continue test, if checkContinue handled there is _not supposed to be_ any request event
couple test cleanups
fix upgrade-head test to send valid request…
make agent test more reliable even if underlying connections get closed for whatever reason
travisplexer: pr-403-arm travis ci test