Add class names param to plot_confusion_matrix

[pokidyshev]

Description

Related issues or pull requests

Pull Request Checklist

• Added a note about the modification or contribution to the ./docs/sources/CHANGELOG.md file (if applicable)
• Added appropriate unit test functions in the ./mlxtend/*/tests directories (if applicable)
• Modify documentation in the corresponding Jupyter Notebook under mlxtend/docs/sources/ (if applicable)
• Ran nosetests ./mlxtend -sv and make sure that all unit tests pass (for small modifications, it might be sufficient to only run the specific test file, e.g., nosetests ./mlxtend/classifier/tests/test_stacking_cv_classifier.py -sv)
• Checked for style issues by running flake8 ./mlxtend

[pep8speaks]

Hello @sandpiturtle! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file mlxtend/plotting/plot_confusion_matrix.py:

Line 100:1: W293 blank line contains whitespace
Line 105:1: W293 blank line contains whitespace

Comment last updated at 2019-03-27 19:09:58 UTC

[coveralls]

Coverage decreased (-0.07%) to 91.543% when pulling 170ffa2 on sandpiturtle:master into 5016a00 on rasbt:master.

[rasbt]

Thanks for the PR. This is a nice addition according to the discussion in #485

Since there are no unit tests for plotting visualizations, could you please add an example in the documentation (at the bottom of https://github.com/rasbt/mlxtend/blob/master/docs/sources/user_guide/plotting/plot_confusion_matrix.ipynb ; these jupyter notebooks are used to render the HTML documentation upon a new version release)

Also, it would be nice if you could make an entry in the Changelog.