add PDF vignette to CRAN
diff --git a/vignettes/header.tex b/vignettes/header.tex
new file mode 100644
index 0000000..95730ec
--- /dev/null
+++ b/vignettes/header.tex
@@ -0,0 +1,6 @@
+\usepackage{booktabs}
+\usepackage{longtable}
+\usepackage{array}
+\usepackage{multirow}
+\usepackage[table]{xcolor}
+\usepackage{wrapfig}