TST: suppress gratuitous warnings
VIS: Hide labels for NaN/zeros in boxplt

[ci skip]
BUG: Bug in alignment with TimeOps and non-unique indexes (GH8363)
Merge pull request #8364 from jreback/datetime_ops

BUG: Bug in alignment with TimeOps and non-unique indexes (GH8363)
BUG: rolling_window() properly averages weights in mean=True mode; removed scikits-timeseries dependency for testing; added further tests for rolling_window()
Merge pull request #8238 from stahlous/win_weights

BUG: normalize rolling_window() weights, remove scikits-timeseries dependency for testing
BUG/COMPAT: set tz on DatetimeIndex on pickle reconstruction (GH8367)
BUG: OLS with clustering and nw_lags does not error (GH5884)

Added statement to raise ValueError when OLS is run with clustering and
Newey-West adjustments. Closes GH5884.
BUG: to_clipboard output formatting (GH8305)
Merge pull request #8370 from jreback/tz_pickle

BUG/COMPAT: set tz on DatetimeIndex on pickle reconstruction (GH8367)
Merge pull request #8299 from seth-p/test_moments_warnings

TST: suppress gratuitous warnings in test_moments.py
API/FIX: wrap result cut/qut in Series and make it ordered

As per the discussion in #8077, the result of cut/qcut should be
wrapped into a Series, now that this is possible.

Also change the returned Categorical to "ordered=True", this was
overlooked when this was introduced in Categorical.

Closes: #8077
TST: 32-bit fix related GH8364
BUG: bug in non-evently divisible offsets when resampling (e.g. '7s') (GH8371)
API: .fillna will now raise a NotImplementedError when passed a DataFrame (GH8377)
Merge pull request #8378 from jreback/fillna_err

API: .fillna will now raise a NotImplementedError when passed a DataFrame (GH8377)
non-existent columns in DataFrame.dropna subset argument now raises KeyError
EHN: Allow DataFrame.fillna to accept a DataFrame as its fill value.
FIX: Implement small Categorical fixups

This is a squashed commit which adresses several small issues
identified in the latest code review.

* As per dicussion in https://github.com/pydata/pandas/issues/8074,
  Categorical.unique() should return an array and not a Index object
  to make is consistant with other unique() implementations.

* Mark a few more categorical methods as internal

* Change reorder_levels and drop_unused_levels to inplace=False. As per
  the discussion in #8074, change the default of both methods
  to return a copy and only do the change inplace if told otherwise.

  Discusion in
  https://github.com/pydata/pandas/issues/8074#issuecomment-54093664

* Make str(cat) more array like. As Categorical is more like
  np.ndarray and less similar to pd.Series, change the string
  representation of Categorical to be more like np.ndarray.

  The new str(cat) will only show at max 10 values.

  Also remove the "Categorical(" in front of an empty categorical
  -> either that's put in front of every str(cta) or none. It also missed
  the final ")".

* Test more nan handling in Categorical

* Add a testcase for groupby with two columns and unused categories

  During the devleopment of pandas new Categorical support, groupby
  with two columns (one worked) didn't include empty categories which
  omits rows with NaN. Add a testcase so this is checked.

  No codechanges nessesary, this bug was fixed at some other places
  before. See #8138 for more details.
API: remove compat keyword in Categorical constructor

Before the new Categorical work, the default two argument constructor
was expecting "codes and levels" but this was changed to
"values and levels" and a 'compat' kwarg was added, which could
be used to switch to the old style constructor useage.

It was decided that we switch to the new style constructor useage as
the new default (compat=False) and implement a 'from_codes(...)'
constructor.

As the compat codepath is now never triggered and code should be
changed to use the new 'from_codes()' constructor, remove the old
codepath.

Add some warnings if we are pretty sure that the old style
constructor is meant, but unfortunately we don't catch all cases.