Added some clarification to the readme.

README.md

@@ -59,6 +59,9 @@ digd.js --input <path/to/dns.json>
 digd.js --input ./samples/db.json
 ```
 
+(For more information on the JSON structure see [JSON Database File](#JSON_DATABASE_FILE) 
+below.)
+
 ### Testing
 
 ```bash