DOC: added examples to mean and fixed quotes
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @rscheiwe! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/core/generic.py`](https://github.com/rscheiwe/pandas/blob/8811b5e2acf1fae4f52af5f883a56f5033ace99c/pandas/core/generic.py) !



##### Comment last updated on October 22, 2018 at 21:14 Hours UTC Ok, fixed those!  Why was `doc/test.parquet` committed? That should have been out of scope of this PR? I'll have to restore and restart. I'm not sure why that pushed. 