Blocked by there being no tests. ;)

What do you think would be good to test here? There's not a lot to this library since it's mostly a wrapper around `gearman-go`. The things that I can think of that would be useful to test:

  1. Verify that the `fn` on a `Worker` properly receives a job - this would basically look like calling `worker.fn(someGearmanWorkerJob)`.
    * PURPOSE: Confirming our weird casting on `New` works
  2. Verify that `Listen` connects to the right host/port and sends the right CAN_DO signal. The only way that I can think of to do this involves starting up a TCP server - any better ideas?
    * PURPOSE: Confirm that we're properly calling `AddServer` and passing the worker name to `AddFunc`
  3. Verify that the worker receiving a `JOB_ASSIGN` signal passes the job to the `JobFun`. The only way that I can think of to do this involves starting up a TCP server - any better ideas?
    * PURPOSE: Confirm that we're properly passing the `JobFunc` to `AddServer` (some overlap with 1)