Update pandas to 0.23.4

[pyup-bot]

This PR updates pandas from 0.23.3 to 0.23.4.

Changelog

0.23.4

------------------------

This is a minor bug-fix release in the 0.23.x series and includes some small regression fixes
and bug fixes. We recommend that all users upgrade to this version.

.. warning::

Starting January 1, 2019, pandas feature releases will support Python 3 only.
See :ref:`install.dropping-27` for more.

.. contents:: What's new in v0.23.4
 :local:
 :backlinks: none

.. _whatsnew_0234.fixed_regressions:

Fixed Regressions
~~~~~~~~~~~~~~~~~

- Python 3.7 with Windows gave all missing values for rolling variance calculations (:issue:`21813`)

.. _whatsnew_0234.bug_fixes:

Bug Fixes
~~~~~~~~~

**Groupby/Resample/Rolling**

- Bug where calling :func:`DataFrameGroupBy.agg` with a list of functions including ``ohlc`` as the non-initial element would raise a ``ValueError`` (:issue:`21716`)
- Bug in ``roll_quantile`` caused a memory leak when calling ``.rolling(...).quantile(q)`` with ``q`` in (0,1) (:issue:`21965`)

**Missing**

- Bug in :func:`Series.clip` and :func:`DataFrame.clip` cannot accept list-like threshold containing ``NaN`` (:issue:`19992`)

Links

• PyPI: https://pypi.org/project/pandas
• Changelog: https://pyup.io/changelogs/pandas/
• Homepage: http://pandas.pydata.org

[coveralls]

Pull Request Test Coverage Report for Build 169

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 77.7%

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Totals
Change from base Build 148:	0.0%
Covered Lines:	777
Relevant Lines:	1000

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💛 - Coveralls