Backport PR #27991 on branch 0.25.x (DataFrame html repr: also follow min_rows setting)
Backport PR #27991: DataFrame html repr: also follow min_rows setting
Hmm, no idea why this is failing here. cc @TomAugspurger 

There are some errors related to the change:

```
__________________ TestDataFrameFormatting.test_repr_min_rows __________________
[gw0] linux -- Python 3.7.4 /home/travis/miniconda3/envs/pandas-dev/bin/python
self = <pandas.tests.io.formats.test_format.TestDataFrameFormatting object at 0x7f1cf575e850>
    def test_repr_min_rows(self):
        df = pd.DataFrame({"a": range(20)})
    
        # default setting no truncation even if above min_rows
        assert ".." not in repr(df)
>       assert ".." not in df._repr_html_()
E       TypeError: argument of type 'NoneType' is not iterable
```

That should only happen (the result being None) if `get_option("display.notebook_repr_html")` gives False. Not sure why that would not be the default here (which is hardcoded to True).

But, there are also a bunch of repr tests failing that are not related to the html repr ..  Hmm strange. I'm able to reproduce on 0.25.x. OK, the return value of `formatter.to_html` changed on master recently (https://github.com/pandas-dev/pandas/pull/27598), and to avoid to need to backpart that PR as well, just pushed a small fix here.