ENH: Add functions for creating dataframes with NaNs
DOC: add explanation to doc/sphinxext
str_extract should work for timeseries, bug 6348
BUG FIX: cartesian_product now converts all arguments to ndarrays

Fixes GitHub issue #6439.
BUG/TST: sorting of NaNs on sym_diff
CLN: remove dead code in pandas.computation
Merge pull request #6448 from cpcloud/eval-coverage

CLN: remove dead code in pandas.computation
Merge pull request #6453 from TomAugspurger/sym_diff_nan3.4

BUG/TST: sorting of NaNs on sym_diff
Merge branch 'fix-cartesian-product' of https://github.com/shoyer/pandas into shoyer-fix-cartesian-product
Merge branch 'str_extract_time_series_bug' of https://github.com/andrewkittredge/pandas into andrewkittredge-str_extract_time_series_bug
BLD: remove pdb from test_strings.py
BLD: add numpy 1.8.x builds as optional
Add references to isnull in notnull docs and vice versa
Merge pull request #6458 from qwhelan/notnull_doc

Add references to isnull in notnull docs and vice versa
Merge pull request #6441 from jorisvandenbossche/doc-sphinxext-readme

DOC: add explanation to doc/sphinxext
COMPAT: infer_freq compat on passing an Index of strings (GH6463)
Merge pull request #6465 from jreback/infer_freq2

COMPAT: infer_freq compat on passing an Index of strings (GH6463)
BUG: split should respect maxsplit when no pat is given
Merge pull request #6467 from cpcloud/str-pat-n-fix-6466

BUG: split should respect maxsplit when no pat is given
DOC: release notes for #6466