DOC: note about query strings in HDFStore selection
Merge pull request #6905 from cpcloud/query-doc

DOC: note about query strings in HDFStore selection
API: update SQL functional api #6300
TST: test new read_sql api
Merge pull request #6867 from jorisvandenbossche/sql-api

API: update SQL functional api (GH6300)
BUG: Panel.pct_change uses different kwargs

Pass `periods` as a positional argument so that
it works for Panels too.
ENH: Implement Panel.pct_change