BLD: fix cythonized msgpack extension in setup.py GH5831
Add pandas cookbook to tutorials (for #5837)
BUG/TST: Fixes isnull behavior on NaT in array. Closes #5443

common._isnull_ndarraylike(...) uses lib.isnullobj to check
nulls/NaN/NaT in ndarray, which in turn relies on util._checknull.
_checknull did not know about NaT, but now lib.isnullobj does, while
still maintaining performance by doing arr[i] only once.

Added a test case test_isnull_nat() to test_common.py and
check for NaT in lib.isnullobj. pd.isnull(np.array([pd.NaT]))
now yields the correct results ([True]).
Merge branch 'master' of https://github.com/commonlisp/pandas into commonlisp-master
DOC: release notes (GH5443)
BUG: bug in `o_datetime when passed a np.nan or integer datelike and a format string (GH5863)
Merge pull request #5864 from jreback/to_datetime

BUG: bug in to_datetime when passed a np.nan or integer datelike and a format string (GH5863)
BLD: enhancements to print_versions.py
DOC: updated compare w r
BLD: make util/print_versions.py standlone as well
Merge pull request #5866 from chappers/r-compare

DOC: Flesh out the R comparison section of docs (GH3980)
Merge pull request #5842 from jvns/patch-1

Add pandas cookbook to tutorials (for #5837)
BLD/DOC: explain how to print_versions() sans repo in CONTRIBUTING.md
DOC: tweaks to CONTRIBUTING.md
DOC: show the Panel.reindex API change in v0.13.0.txt (GH5867)
BLD: fixup setup.py, initialize pipe variable to None
Merge pull request #5868 from y-p/PR_setup_pipe

BLD: fixup setup.py, initialize pipe variable to None
BUG: Bug in groupby dtype conversion with datetimelike (GH5869)
Merge pull request #5870 from jreback/groupby_ts

BUG: Bug in groupby dtype conversion with datetimelike (GH5869)
BLD: python3 unicode issue in print_versions