Allow bulk configs to be overridable via mix tasks

[imranismail]

config :recommender, Recommender.Elasticsearch.Cluster,
  # When indexing data using the `mix elasticsearch.build` task,
  # control the data ingestion rate by raising or lowering the number
  # of items to send in each bulk request.
  bulk_page_size: 5000,

  # Likewise, wait a given period between posting pages to give
  # Elasticsearch time to catch up.
  # 15 seconds
  bulk_wait_interval: 15_000,

Something like this:

mix elasticsearch.build users --cluster Recommender.Elasticsearch.Cluster --wait-interval 15000 --page-size 5000

On top of that. Allowing it to be configured per index level would also be nice.

[imranismail]

Wow that was fast!

Thank you @danielberkompas

[danielberkompas]

No problem! I released v0.4.0 with this change.