DOC: update the pandas.Series.str.strip docstring
- [ ] closes #xxxx
- [ ] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @Cheukting! Thanks for updating the PR.



Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on July 07, 2018 at 20:05 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20863?src=pr&el=h1) Report
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Docstring for "pandas.Series.str.strip" correct. :) Hi @Cheukting, great work! As @datapythonista pointed out in #20897, it seems that our wires crossed during the sprint and we ended up working on the same thing. 

Seeing as this PR got in earlier, please feel free to grab anything from our PR that might help address Marc's notes, and we'll close ours. If you don't plan to refine this PR, please let us know and we'll continue on #20897.  Thanks @alsobay and @jalammar! I really like your PR and I think I may borrow some ideas and put it here. Feel free to keep commenting and reviewing this PR as it is our collaboration effort :-) Looks great! Will merge on green. @mroeschke merge away Thanks @Cheukting! 