GH-33 - Adding method status to FixedThreadPool.

The method `status` was accidentally removed a few months ago, this is a
deprecated method and we gonna have to remove it soon, but for now we're
adding the method back with a warn message saying that this is a
deprecated method.
GH-33 - Added specs to CachedThreadPool#status and FixedThreadPool#status
Merge pull request #47 from jdantonio/gh-33

Gh 33 - Adding method #status to FixedThreadPool