ENH: DataFrame.explode() multiple columns
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @stahl085! Thanks for opening this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

* In the file [`pandas/core/frame.py`](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py):

> [Line 6264:68](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6264): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6272:35](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6272): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6273:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6273): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6274:34](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6274): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6282:23](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6282): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6284:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6284): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6288:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6288): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6291:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6291): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6294:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6294): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6297:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6297): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6298:28](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6298): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 6298:40](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6298): [E261](https://duckduckgo.com/?q=pep8%20E261) at least two spaces before inline comment
> [Line 6300:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6300): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6303:14](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6303): [E225](https://duckduckgo.com/?q=pep8%20E225) missing whitespace around operator
> [Line 6303:59](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6303): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 6303:76](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6303): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6304:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6304): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6307:44](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6307): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 6308:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6308): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 6315:1](https://github.com/pandas-dev/pandas/blob/816d22c542ee9dcff9c9fda28e292933328dec75/pandas/core/frame.py#L6315): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace

 Whoops PR my wrong branch, brb