updated description with thomas leeper

DESCRIPTION

@@ -6,10 +6,13 @@ Authors@R: c(person(c("Tyson", "S"), "Barrett", email = "t.barrett@aggiemail.usu
              person("Angelo", "Canty", role = c("ctb"), 
                     comment = "S original bootstrap method, http://statwww.epfl.ch/davison/BMA/library.html"),
              person(c("Brian", "D."), "Ripley", role = c("ctb"),
-                    comment = "R port, bootstrap method", email = "ripley@stats.ox.ac.uk"))
+                    comment = "R port, bootstrap method", email = "ripley@stats.ox.ac.uk"),
+             person("Thomas", "Leeper", role = c("ctb"),
+                    comment = "Vectorized marginal effects, https://thomasleeper.com/software.html"))
 Description: Provides the ability to perform "Marginal Mediation"--mediation
    wherein the indirect and direct effects are in terms of the average marginal effects 
    (Bartus, 2005, <https://EconPapers.repec.org/RePEc:tsj:stataj:v:5:y:2005:i:3:p:309-329>). 
+   The style of the average marginal effects stems from Thomas Leeper's work on `margins`.
    This framework allows the use of categorical mediators and outcomes with little change in interpretation
    from the continuous mediators/outcomes. See <doi:10.13140/RG.2.2.18465.92001> for more details 
    on the method (peer reviewed articles forthcoming).