Rename config sample to config.example.php, update comments

config.example.php

@@ -1,8 +1,8 @@
 <?php
 /**
- * Site config. KEEP THIS FILE PRIVATE — if this project ever goes under
- * git, add config.php to .gitignore before committing anything, since
- * FB_PAGE_ACCESS_TOKEN is a secret.
+ * Site config template — tracked in git, safe to commit (no real secret
+ * here). Copy this file to config.php (gitignored) and fill in your own
+ * FB_PAGE_ACCESS_TOKEN there.
  */
 
 // Base URL the site is currently reachable at. Used for social sharing