move the tree rendering steps to lib/page-data which happens during warm-server

lib/warm-server.js

@@ -44,8 +44,12 @@ async function warmServer () {
     unversionedTree = await dog.loadUnversionedTree()
   }
 
+  if (!site) {
+    site = dog.loadSiteData()
+  }
+
   if (!siteTree) {
-    siteTree = await dog.loadSiteTree(unversionedTree)
+    siteTree = await dog.loadSiteTree(unversionedTree, site)
   }
 
   if (!pageList) {
@@ -56,10 +60,6 @@ async function warmServer () {
     pageMap = await dog.loadPageMap(pageList)
   }
 
-  if (!site) {
-    site = dog.loadSiteData()
-  }
-
   if (!redirects) {
     redirects = await dog.loadRedirects(pageList)
   }