Job retries

```javascript
queue.enqueue(
  'retry', 
  { test: 'data' }, 
  { 
    attempts: {
      count: 2, //Pass in the number of times you want the job to be retried
      delayMS: 50, // (Optional) Pass in the number of milliseconds to wait before retrying.
      delayStrategy: 'exponential', // (Optional) Pass in the delay strategy to use. Default is "linear"
      delayFunction: function(job) { ... } // (Optional) Pass in a function to compute the delay
    }
  }, 
  done
);
```