DEPR: Deprecate pandas.np module
- [x] closes #30296 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry


Hello @lithomas1! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:









There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-12-26 02:00:49 UTC > py36 needs to be handled separately

You can still do the `import numpy as np` in the `else` clause.

Can you also add tests for this? (that it still works but generates a warning for py37) @jbrockmendel and @jorisvandenbossche 
Can you take another look at the code? I added tests and made the deprecation warnings also show on Python 3.6  ping @jreback 
CI has passed.  thanks @lithomas1 very nice!