add module auxiliary/dos/http/nodejs_pipeline

Add a HTTP DoS module for the recent Node.js vulnerability.
Simply flood requests pipelined over a single connection until the server runs out of memory.

I really hadn't to do a lot of work. (First module, don't be too harsh)

Not sure if I should stop when the server becomes unresponsive or what.

Here is the nodejs issue joyent/node#6214 ([cache](http://webcache.googleusercontent.com/search?rlz=1C5CHFA_enIT503IT503&espv=210&es_sm=91&sclient=psy-ab&q=cache%3Ahttps%3A%2F%2Fgithub.com%2Fjoyent%2Fnode%2Fissues%2F6214&oq=cache%3Ahttps%3A%2F%2Fgithub.com%2Fjoyent%2Fnode%2Fissues%2F6214&gs_l=serp.12...0.0.1.6345.0.0.0.0.0.0.0.0..0.0)), the [commit](joyent/node/commit/085dd30e93da67362f044ad1b3b6b2d997064692) (includes a PoC) and the [advisory](https://groups.google.com/forum/#!topic/nodejs/NEbweYB0ei0) (no CVE).