replaced pandas.plotting with pandas.tools.plotting
 - [x] closes #16754 
 - [x] tests added / passed - mentioned in #16754 
 - [ ] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [x] whatsnew entry - Going through [Visualization](https://pandas-docs.github.io/pandas-docs-travis/visualization.html) in search of beautiful plots I came across the issue, I'm new to Open source so critics are welcome, for this amateurish attempt.  
