code: function send(payload, promise) {
  	if (typeof apostle.domainKey == 'undefined'){
  		promise.reject('invalid', [{error: 'No domain key defined. Please set a domain key with `apostle.domainKey = "abc123"`'}])
  		return;
  	}
  	(request || superagent)
  		.post(apostle.deliveryEndpoint)
  		.type('json')
  		.send(payload)
  		.set('Authorization', 'Bearer ' + apostle.domainKey)
  		.set('Apostle-Client', 'JavaScript/v0.1.1')
  		.end(function(err, res){
  			if(res.ok){
  				promise.fulfill()
  			}else{
  				promise.reject('error', res)
  			}
  		})
  }
docs: Delivery the JSON payload to the delivery endpoint via Request.
  
  @param {object} Recipient Payload
  - recipients {object} Email => data object of recipient information
  @param {promise} Deferred promise object
  
  @return {null}