API throttling

[rclark]

I noticed some throttling messages sneaking into the console on a search with a very large number of results, along the lines of

> sumo --query '_sourceCategory = my-thing' --from 4d

{ [HTTPError: Response code 429 (Too Many Requests)]
  message: 'Response code 429 (Too Many Requests)',
  host: 'api.sumologic.com',
  hostname: 'api.sumologic.com',
  method: 'GET',
  path: '/api/v1/search/jobs/4FD8AA773A30EAD6',
  statusCode: 429,
  statusMessage: 'Too Many Requests' }

The search continued to return results.