elastic v0.6.0

Compatibility for many Elasticsearch versions has improved. We've tested on ES versions
from the current (v2.1.1) back to v1.0.0, and elastic works with all versions.
There are some functions that stop with a message with some ES versions simply
because older versions may not have had particular ES features. Please do let us
know if you have problems with older versions of ES, so we can improve compatibility.

NEW FEATURES

• Added index_settings_update() function to allow updating index settings (#66)
• All errors from the Elasticsearch server are now given back as JSON.
  Error parsing has thus changed in elastic. We now have two levels of error
  behavior: 'simple' and 'complete'. These can be set in connect() with the
  errors parameter. Simple errors give back often just that there was an error,
  sometimes a message with explanation is supplied. Complete errors give
  more explanation and even the ES stack trace if supplied in the ES error
  response (#92) (#93)
• New function msearch() to do multi-searches. This works by defining queries
  in a file, much like is done for a file to be used in bulk loading. (#103)
• New function validate() to validate a search. (#105)
• New suite of functions to work with the percolator service: percolate_count(),
  percolate_delete(), percolate_list(), percolate_match(), percolate_register().
  The percolator works by first storing queries into an index and then you define
  documents in order to retrieve these queries. (#106)
• New function field_stats() to find statistical properties of a field without
  executing a search (#107)
• Added a Code of Conduct
• New function cat_nodeattrs()
• New function index_recreate() as a convenience function that detects if an
  index exists, and if so, deletes it first, then creates it again.

MINOR IMPROVEMENTS

• docs_bulk() now supports passing in document ids (to the _id field)
  via the parameter doc_ids for each input data.frame or list & supports using ids
  already in data.frame's or lists (#83)
• cat_*() functions cleaned up. previously, some functions had parameters
  that were essentially silently ignored. Those parameters dropped now
  from the functions. (#96)
• Elasticsearch had for a while 'search exists' functionality (via /_search/exists),
  but have removed that in favor of using regular _search with size=0 and
  terminate_after=1 instead. (#104)
• New parameter lenient in Search() and Search_uri to allow format based
  failures to be ignored, or not ignored.
• Better error handling for docs_get() when gthe document isn't found

BUG FIXES

• Fixed problems in docs_bulk() in the use case where users use
  the function in a for loop, for example, and indexing started over,
  replacing documents with the same id (#83)
• Fixed bug in cat_() functions in which they sometimes failed
  when parse=TRUE (#88)
• Fixed bug in docs_bulk() in which user supplied document IDs weren't being
  passed correctly internally (#90)
• Fixed bug in Search() and Search_uri() where multiple indices weren't
  supported, whereas they should have been - supported now (#115)

DEFUNCT

• The following functions are now defunct: mlt(), nodes_shutdown(), index_status(),
  and mapping_delete() (#94) (#98) (#99) (#110)