Update SpeakerMailer for engine-style email configuration

[reidab]

Currently, the OCW mailer makes assumptions about what's going to be configured that don't match well with what actually gets configured by the host app, especially in Speaker#mailer.configured?

[reidab]

A workaround:

1. Configure ActionMailer in your config/environments/*.rb files, per http://guides.rubyonrails.org/action_mailer_basics.html#action-mailer-configuration
2. Edit config/initializers/01_open_conference_ware.rb to include the config that OCW expects to see:

# Set the default address from which to send outgoing mail
config.default_from_address = "you@yourdomain.org"

# Set an address to BCC on all outbound communication (optional)
config.default_bcc_address = "you@yourdomain.org"

# Fulfill the expectations of SpeakerMailer.configured?
config.email = {
  "action_mailer" = {"enabled" => true}
  "default_from_address" = config.default_from_address
}

[kuwaharg]

Correction on the config.email setting in the 01_open_conference_ware.rb file. It should be:

# Fulfill the expectations of SpeakerMailer.configured?
config.email = {
  "action_mailer" => {"enabled" => true},
  "default_from_address" => config.default_from_address
}