add support for wildcard indices

[jxstanford]

would be nice to be able to support getting from a pattern of indices. one example for this would be something like the logstash-%Y%d%m style indexing. I generally keep an alias pointing at the index that I want to write to, so you could express a model to index mapping in a way similar to:

{"thing1": {"read": "my_daily_*", "write": "my_daily"}}