address PR comments

Author: backuitist

overviews/core/_posts/2012-09-20-futures.md

@@ -11,9 +11,9 @@ languages: [ja]
 
 ## Introduction
 
-Futures provide a nice way to reason about performing many operations
-in parallel-- in an efficient and non-blocking way. The idea
-is simple, a [Future](http://www.scala-lang.org/api/current/index.html#scala.concurrent.Future) 
+Futures provide a way to reason about performing many operations
+in parallel-- in an efficient and non-blocking way. 
+A [Future](http://www.scala-lang.org/api/current/index.html#scala.concurrent.Future) 
 is a sort of a placeholder object that you can create for a result that does not yet exist. 
 Generally, the result of the `Future` is computed concurrently and can be later collected.
 Composing concurrent tasks in this way tends to result in faster, asynchronous, non-blocking parallel code.