doc: fix minor grammar mistake in streams docs
doc: fix minor grammar mistake in streams docs

PR-URL: https://github.com/iojs/io.js/pull/606
Reviewed-By: Rod Vagg <f9f03903429036ef609ed7ca822fddfa76155c29@vagg.org>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node