Fix default values of arguments to follow Rails convention

Fix default spacing in actionmailer delivery methods
```ruby
def add_delivery_method(symbol, klass, default_options = {})
        class_attribute(:"#{symbol}_settings") unless respond_to?(:"#{symbol}_settings")
        send(:"#{symbol}_settings=", default_options)
        self.delivery_methods = delivery_methods.merge(symbol.to_sym => klass).freeze
end

def wrap_delivery_behavior(mail, method = nil, options = nil) # :nodoc:
  method ||= self.delivery_method
  mail.delivery_handler = self

  case method
  when NilClass
    raise "Delivery method cannot be nil"
  when Symbol
    if klass = delivery_methods[method]
      mail.delivery_method(klass,(send(:"#{method}_settings") || {}).merge!(options || {}))
    else
      raise "Invalid delivery method #{method.inspect}"
    end
  else
    mail.delivery_method(method)
  end

  mail.perform_deliveries    = perform_deliveries
  mail.raise_delivery_errors = raise_delivery_errors
end
```