title: elasticdump can't import data from file
body: <p>I tried import data from json file. Use command like this: 
  <code>elasticdump --input=2016-1-1-2016-7-31-2.json --output=http://localhost:9200/</code> And format like this: <a href="https://github.com/taskrabbit/elasticsearch-dump/blob/master/test/seeds.json" rel="nofollow noreferrer">https://github.com/taskrabbit/elasticsearch-dump/blob/master/test/seeds.json</a> 
  My backup file has few indexes. But when I start command which I wrote above - got result like this:
  <code>
  Fri, 13 Apr 2018 13:36:44 GMT | starting dump
  Fri, 13 Apr 2018 13:36:44 GMT | got 100 objects from source file (offset: 0)
  Fri, 13 Apr 2018 13:36:44 GMT | sent 100 objects to destination elasticsearch, wrote 0
  Fri, 13 Apr 2018 13:36:44 GMT | got 291 objects from source file (offset: 100)
  Fri, 13 Apr 2018 13:36:44 GMT | sent 291 objects to destination elasticsearch, wrote 0
  Fri, 13 Apr 2018 13:36:44 GMT | got 292 objects from source file (offset: 391)
  Fri, 13 Apr 2018 13:36:45 GMT | sent 292 objects to destination elasticsearch, wrote 0
  Fri, 13 Apr 2018 13:36:45 GMT | got 293 objects from source file (offset: 683)
  </code>
  If I set index name in URL or through --output-index={INDEX} - all data from file go to that index with separating on types.</p>
  
  <p>I will be grateful for the help!</p>