Allow raw bulk indexing via Elasticsearch::Index
Bulk Loader which can read data from stdin

This also works by inserting data into a disconnected index alias before
switching over. The old index is locked during indexing so index workers
will be queued (and retry every 60 seconds).
Improve logging and send even sized chunks

Send in chunks of 1MB
More explicit load_path variable name
Better help on CLI
Add unit test for bulk loader batch splitting

and explanatory comment
Merge pull request #161 from alphagov/fast-bulk-loading

Fast bulk loading