"inst" in package skeleton causes R CMD check WARNING

[colinasmith]

Having "inst" in the following line of roxygenize:

skeleton <- c(roxygen.dir, file.path(roxygen.dir, c("man", "inst")))

causes a warning in R CMD check if the directory is empty:

• checking package subdirectories ... WARNING
  Subdirectory ‘inst’ contains no files.

[hadley]

Fixed in 179448a