Added a Decider.


git-svn-id: http://scalatest.googlecode.com/svn/trunk@5000 fd1274fd-080f-5963-8033-43ee40fcd1de
Rename Deciders trait to Explicitly.


git-svn-id: http://scalatest.googlecode.com/svn/trunk@5001 fd1274fd-080f-5963-8033-43ee40fcd1de