added support for estimated date in DHL

[sailrish]

And released as shipit 1.2.0. http://shipit-api.herokuapp.com/api/carriers/dhl/2628987793

{  
   "eta":"2019-02-05T07:59:00.000Z",
   "weight":"7.56 LB",
   "destination":"Van Nuys, CA, USA",
   "activities":[  
      {  
         "timestamp":"2019-01-31T02:24:58.000Z",
         "location":"Hong Kong, HKG",
         "details":"Departed Facility"
      },
      {  
         "timestamp":"2019-01-31T01:51:03.000Z",
         "location":"Hong Kong, HKG",
         "details":"Processed"
      },
      {  
         "timestamp":"2019-01-30T20:42:43.000Z",
         "location":"Hong Kong, HKG",
         "details":"Arrived at Sort Facility"
      },
      {  
         "timestamp":"2019-01-30T18:39:00.000Z",
         "location":"Los Angeles, CA, USA",
         "details":"Customs status updated"
      },
      {  
         "timestamp":"2019-01-30T15:12:43.000Z",
         "location":"Hong Kong, HKG",
         "details":"Shipment picked up"
      }
   ],
   "status":2,
   "request":{  
      "trackingNumber":"2628987793"
   }
}