[bug 873635] Fix index_chunk and esreindex output

* fix index_chunk to break up the documents to bulk index in small
  chunks
* fix recreate_index to wait until a shard is yellow before continuing
* fix esreindex command output so the deltas and ETAs are more correct

Way to test this:

1. run the unit tests
2. generate a bunch of sample data (`./manage.py generatedata --with=samplesize=1000` a few times)
3. run `./manage esreindex`
4. change CELERY_ALWAYS_EAGER = False
5. run celery in one window and the webserver in another
6. reindex from the admin

If all that works, then this is kosher.

r?