Numpy version incompatibility
#### Code Sample, a copy-pastable example if possible

```python
Python 3.6.7 (v3.6.7:6ec5cf24b7, Oct 20 2018, 13:35:33) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas as pd
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\SoftInstall\Python\lib\site-packages\pandas\__init__.py", line 31, in <module>
    from pandas._libs import hashtable as _hashtable, lib as _lib, tslib as _tslib
  File "D:\SoftInstall\Python\lib\site-packages\pandas\_libs\__init__.py", line 3, in <module>
    from .tslibs import (
  File "D:\SoftInstall\Python\lib\site-packages\pandas\_libs\tslibs\__init__.py", line 3, in <module>
    from .conversion import localize_pydatetime, normalize_date
  File "__init__.pxd", line 918, in init pandas._libs.tslibs.conversion
ValueError: numpy.ufunc size changed, may indicate binary incompatibility. Expected 216 from C header, got 192 from PyObject
```
#### Problem description

Although Pandas 1.0.1 has a minimum requirement for numpy of 1.13.3 ([see release notes of Pandas 1.0.0](https://pandas.pydata.org/docs/whatsnew/v1.0.0.html#increased-minimum-versions-for-dependencies)), it fails with numpy 1.15.4 (Python 3.6.7).

Problem is solved by upgrading numpy (version 1.18.1 works).
