Plotting ExtensionArrays
- [x] closes #26173
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

How do I go about adding tests for that rely on an external module?
Would be something like
```python3
df = pd.DataFrame({
        "length" : pd.Series([1,2],dtype = pd.Int16Dtype),
        "width" : PA_([2,3], dtype="pint[m]"),
        "distance" : PA_([2,3], dtype="in"),
        "height" : PA_([2,3], dtype=ureg.m),
        "depth" : PA_.from_1darray_quantity(Q_([2,3],ureg.mm)),
    })
df.plot()
```
Hello @andrewgsavage! 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 2019-06-30 07:12:34 UTC I'm a bit confused here, df.select_dtypes('number') will not return columns with bool dtype. However is_numeric_dtype(dtype) will return True for bool. Should is_numeric_dtype be used in select_dtypes? can you merge master Nice idea but looks like this has gone stale and I think has a few dependencies that need to be cleaned up. In any case @andrewgsavage if interested in continuing please ping and can reopen