Add support for outgoing mail handling.

Methods
Classes and Modules
Module Nitro::OutgoingMailer::ClassMethods
Attributes
[RW] template_dir The root directory where the templates reside.
Public Class methods
new(from = nil, to = nil, subject = nil, body = MailTemplate.new)
    # File lib/nitro/mailer/outgoing.rb, line 17
17:   def initialize(from = nil, to = nil, subject = nil, body = MailTemplate.new)
18:     super
19:     @charset = Mailer.default_charset.dup
20:     @encode_subject = Mailer.encode_subject
21:     @template_dir = Mailer.template_dir
22:   end