Allow null configuration

 import web
 
 app = web.application(__name__, automount=True, autotemplate=True)
-host_name = app.cfg["host_name"]
-stripe.api_key = app.cfg["stripe_sk"]
+host_name = app.cfg.get("host_name")
+stripe.api_key = app.cfg.get("stripe_sk")
 
 
 @app.control("")

 
 understory = web.application("understory")
 
-admin_name = understory.cfg["admin_name"]
-admin_domain = understory.cfg["admin_domain"]
-stripe_pk = understory.cfg["stripe_pk"]
+admin_name = understory.cfg.get("admin_name")
+admin_domain = understory.cfg.get("admin_domain")
+stripe_pk = understory.cfg.get("stripe_pk")