added reference to original article in description

DESCRIPTION

@@ -9,7 +9,7 @@ Authors@R: c(person("Nathaniel", "Phillips", role = c("aut", "cre"),
               person("Jan", "Woike", role = "aut"),
               person("Wolfgang", "Gaissmaer", role = "aut"))
 Maintainer: Nathaniel Phillips <Nathaniel.D.Phillips.is@gmail.com>
-Description: Create, visualize, and test fast-and-frugal decision trees (FFTs). FFTs are very simple decision trees for
+Description: Create, visualize, and test fast-and-frugal decision trees (FFTs) using methods described in Phillips, Neth, Woike & Gaissmaier. (2017). FFTs are very simple decision trees for
     binary classification problems. FFTs can be preferable to more complex algorithms because they are easy to communicate, 
     require very little information, and are robust against overfitting.
 LazyData: TRUE