Recommend turning off raise delivery errors

Folks may not always want MailCatcher running, and don't want errors
raised during mail delivery if it's not.

README.md

@@ -48,6 +48,7 @@ To set up your rails app, I recommend adding this to your `environments/developm
 
     config.action_mailer.delivery_method = :smtp
     config.action_mailer.smtp_settings = { :address => "localhost", :port => 1025 }
+    config.action_mailer.raise_delivery_errors = false
 
 ### PHP