streams2 write stream

[ghost]

This is the writeable stream component for the streams2 issue #161 to go along with pull #176. The api is no longer requires listening for a ready event before being able to call .end(), .destroy(), and .destroySoon().

BEFORE (75104e0):

$ node stream-bench.js 
--------------------------------------------------------------
Filled source! Took 35280ms, streaming to destination...
Done! Took 36435ms, 103% of batch time

AFTER (15c53d7):

$ node stream-bench.js 
--------------------------------------------------------------
Filled source! Took 34257ms, streaming to destination...
Done! Took 36344ms, 106% of batch time

There is a minor slowdown but it might just be noise.

[pgte]

@substack There is a PR for revamping the writeStream implementation based on streams2.
This PR takes what @rvagg did on the write-stream-optimization-benchmark branch regarding performance and matches up.

It would be useful if you could compare this PR to the performance of any of these branches?
Also, is there any feature in my PR that this PR covers?

Thanks!

[juliangruber]

@substack needs simple-bufferstream dependency

[rvagg]

simple-bufferstream is only for fstream support which needs to be removed completely when a writestream replacement is merged