Support Multiple Worker Types

[robertomiranda]

I was wondering if with the current API is possible to add more Worker with different type to an existing Server? If this is not possible what do you think about the following chunk of code?

se = ServerEngine.create(nil, MyWorker1, {
  daemonize: true,
  log: 'myserver.log',
  pid_path: 'myserver.pid',
  worker_type: 'process',
  workers: 2,
})

se.add_worker(MyWorker2)
se.add_worker(MyWorker2)
se.add_worker(MyWorker2)
se.run

This code launch workers like show the next diagram:

                              +---------+
                   +----------+MyWorker1|
                   |          +---------+
                   |                     
                   |          +---------+
                   |   +------+MyWorker1|
                   |   |      +---------+
+---------+     +--+---+                 
|Superviso+-----+Server+----------------+
+---------+     +-+----+      |MyWorker2|
                  |    |      +---------+
                  |    |                 
                  |    |      +---------+
                  |    +------+MyWorker2|
                  |           +---------+
                  |                      
                  |           +---------+
                  +-----------+MyWorker2|
                              +---------+

[robertomiranda]

cc @frsyuki