Add info

info queries Elasticsearch for version number and some other things.
This adds that and also fixes _add_es_kwarg_docs to handle the case
where there aren't args or query params.
Merge pull request #108 from willkg/106-info

Add info command.
Update index.rst

Added the missing import line.
Merge pull request #112 from konarkmodi/patch-1

Update index.rst
merge with upstream