HTTP js implementation

[jasnell]

@mscdex had started this a while back... nodejs/node#1457

At this point the effort has largely stalled out. It's likely something that we should revisit.

[trevnorris]

If performance is the goal then it should be reassessed whether moving this to JS will achieve that. The C parser is much faster, but the issue is the boundary between JS and C. Though I've been investigating, and have landed a couple PR's, to get around that issue.