Fixed citation

Author: robjhyndman

inst/CITATION

@@ -26,7 +26,7 @@ bibentry(bibtype = "Article",
   title     = "Automatic time series forecasting: the forecast package for {R}",
   author    = c(as.person("Rob J Hyndman"),as.person("Yeasmin Khandakar")),
   journal   = "Journal of Statistical Software",
-  volume    =  26,
+  volume    =  27,
   number    =  3,
   pages     = "1--22",
   year      =  2008,