Completed contain matchers refactoring to require at least 2 arguments in Matchers.scala.
Enhanced only contain matcher to provide friendly reminder when it fails and only single GenTraversable argument is passed in.
Completed contain matchers refactoring to require at least 2 arguments in ContainWord.scala, Matcher.scala and GenFactories.scala.
Completed contain matchers refactoring to require at least 2 arguments in ResultOfContainWord.scala.