TST: change deprecation mode naming in PANDAS_TESTING_MODE, enable for 3.4 build
ENH nlargest and nsmallest Series methods
DOC/REF: add docstrings and DRY it up
DOC: doc blurb in basics.rst
Merge pull request #7113 from cpcloud/hayd-kth_smallest

ENH: add nlargest nsmallest to Series
TST: disable PyTables PANDAS_TESTING_MODE - too many warnings
TST: remove complex256 tests from nlargest/nsmallest
TST: also skip datetime_NaT tests for sqlite3

- tests were failing on some combination of platform/version, see #7100, so skip for now until real solution is implemented
ENH/VIS: kde plot can be cumulative