Add vignettes
diff --git a/docs/docs.Rproj b/docs/docs.Rproj
new file mode 100644
index 0000000..8e3c2eb
--- /dev/null
+++ b/docs/docs.Rproj
@@ -0,0 +1,13 @@
+Version: 1.0
+
+RestoreWorkspace: Default
+SaveWorkspace: Default
+AlwaysSaveHistory: Default
+
+EnableCodeIndexing: Yes
+UseSpacesForTab: Yes
+NumSpacesForTab: 2
+Encoding: UTF-8
+
+RnwWeave: Sweave
+LaTeX: pdfLaTeX