doc: fixed punctuation

Period ending a sentence should be outside parens

PR-URL: https://github.com/iojs/io.js/pull/476
Reviewed-By: Rod Vagg <rod@vagg.org>

README.md

@@ -15,7 +15,7 @@ compatible with the npm ecosystem that has been built to date for Node.js.
 The official name is **io.js**, which should never be capitalized,
 especially not at the start of a sentence, unless it is being
 displayed in a location that is customarily all-caps (such as
-the title of man pages.)
+the title of man pages).
 
 ## To build: