Store Scrapy stats

[adilsoncarvalho]

Find a way to store the Scrapy stats (they're inside the log file)

Crawling stats as JSON metadata

{  
   "downloader/request_bytes":1364,
   "downloader/request_count":2,
   "downloader/request_method_count/GET":2,
   "downloader/response_bytes":33050,
   "downloader/response_count":2,
   "downloader/response_status_count/200":2,
   "finish_reason":"finished",
   "finish_time":"2016-11-28T21:16:39.194838",
   "httpcache/firsthand":2,
   "httpcache/miss":2,
   "httpcache/store":2,
   "item_scraped_count":1,
   "log_count/DEBUG":4,
   "log_count/INFO":8,
   "request_depth_max":1,
   "response_received_count":2,
   "scheduler/dequeued":2,
   "scheduler/dequeued/memory":2,
   "scheduler/enqueued":2,
   "scheduler/enqueued/memory":2,
   "start_time":"2016-11-28T21:16:38.344320"
}