Update pkgdown settings

_pkgdown.yml

@@ -1,14 +1,30 @@
+url: https://purrr.tidyverse.org
+
 template:
   package: tidytemplate
   default_assets: false
 
 home:
   strip_header: true
-
   links:
   - text: Learn more
     href: http://r4ds.had.co.nz/iteration.html
 
+navbar:
+  structure:
+    left:  [home, reference, news]
+    right: [github]
+  components:
+    news:
+      text: News
+      menu:
+      - text: "Release notes"
+      - text: "Version 0.2.3"
+        href: https://www.tidyverse.org/articles/2017/08/purrr-0.2.3/
+      - text: "------------------"
+      - text: "Change log"
+        href: news/index.html
+
 reference:
 - title: Map family
   desc: |