set dns_action as default add

remove api key and secret from defaults

README.md

@@ -20,7 +20,7 @@ dns_records:
   - record_name
     record_value
     record_type
-dns_action: delete or add
+dns_action: delete or add (default add)
 
 Dependencies
 ------------
@@ -50,4 +50,4 @@ BSD
 Author Information
 ------------------
 
-An optional section for the role authors to include contact information, or a website (HTML is not allowed).
+Thomas C <thomas@opendoor.fr>