__or__ (and others?) should return NotImplemented for custom classes
#### Code Sample, a copy-pastable example if possible

```python
In [1]: class Test:
   ...:     def __ror__(self, other):
   ...:         print('here')
   ...:         return self
   ...: 

In [2]: {} | Test()
here
Out[2]: <__main__.Test at 0x7f37a1601ba8>

In [3]: import pandas

In [4]: pandas.DataFrame() | Test()
Out[4]: 
Empty DataFrame
Columns: []
Index: []
```
#### Problem description

I would expect DataFrame to return `NotImplemented` in this case, so we can properly delegate to `__ror__`.

#### Expected Output

```
Out[3]: <__main__.Test at 0x7f37a1601ba8>
```

#### Output of ``pd.show_versions()``

<details>

In [4]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.14.67-ts1
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: en_US.utf8
LOCALE: en_US.UTF-8

pandas: 0.24.2
pytest: 4.4.1
pip: 19.0.3
setuptools: 40.8.0
Cython: 0.29.6
numpy: 1.15.4
scipy: 1.2.1
pyarrow: 0.11.1
xarray: None
IPython: 7.4.0
sphinx: 2.0.1
patsy: 0.5.1
dateutil: 2.8.0
pytz: 2018.9
blosc: None
bottleneck: None
tables: 3.5.1
numexpr: 2.6.9
feather: None
matplotlib: 3.0.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: 1.1.5
lxml.etree: None
bs4: 4.7.1
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: 0.2.0
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None

</details>
