Add missing roxygenize step (ramnathv#370)

* Add missing roxygenize step

* Remove setwd, it's done automatically now

vignettes/develop_intro.Rmd

@@ -278,8 +278,8 @@ This method is highly recommended as it ensures that you get started with the ri
 
 ```r
 devtools::create("mywidget")               # create package using devtools
-setwd("mywidget")                          # navigate to package dir
 htmlwidgets::scaffoldWidget("mywidget")    # create widget scaffolding
+devtools::document()                       # roxygenize, so NAMESPACE is updated
 devtools::install()                        # install the package so we can try it
 ```