DEPR: Series.put, Series.real, Series.imag, Index.dtype_str
- [x] xref #https://github.com/pandas-dev/pandas/issues/18262
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Removes:
`Series.put`
`Index.dtype_str`
`Series.real`
`Series.imag`
Hello @mroeschke! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

























There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-06-28 21:44:10 UTC can you add to the list in #6581 as well Changed to FutureWarnings and green. thanks @mroeschke 