Unable to schedule delivery with the delayed job delivery method

[syntaxTerr0r]

There is no way for providing the 'run_at' argument provided by delayed job. Would be great :)

[holli]

Could be handy in some instances. Easy to do by adding delayed_job to use run_at time if delivery_options[:delayed_job][:run_at] is present. see https://github.com/holli/action_smser/blob/master/lib/action_smser/delivery_methods/delayed_job.rb#L12 and then just setting specific option in the sms.

If you do pull request with tests I'm happy to merge :)