get the vignette working with BiocStyle::pdf_document

[Witold Wolski]

Because of problems with building the vingette on windows we removed BiocStyle::pdf_document
from the vignette header.
However, for bioconductor submission we need it working.

You can build the vingette by:

when in the vignette folder

rmarkdown::render("vignette.Rmd")

when in the project

devtools::build_vignettes()

Should also work when building the package with vignettes.
On the command line you build the package with

R cmd build --help
R cmd build fgcz.gsea.ora