[MRG] DOC make confusion_matrix_plot.py example more copy-pastable

[doshyt]

Reference Issue

Addressed: #6796

What does this implement/fix? Explain your changes.

• Make plot_confusion_matrix.py example more copy-pastable by putting the calculated numbers into the middle of each square on the plot
• Use the list of class names as a parameter of the plotting function

[jnothman]

Can you save us some time by providing an image?

[doshyt]

@jnothman do you mean plots for confusion matrices that the code generates? I was looking for the proper location of these images to put them to the repo but didn't find it. I attach them here, please point me to the correct location if I'm wrong.

[nelson-liu]

I think it would be nice to have a parameter normalize that automatically does the normalizing for the user if set to true, if the intention is to make the example more copy-pastable

also seems like the appveyor failure is spurious on both agramfort's account and the sklearn-ci account. see: https://ci.appveyor.com/project/sklearn-ci/scikit-learn/build/1.0.6980?

[doshyt]

Thanks, @nelson-liu for valuable comments. Indeed, moving the normalization into the function body seems like a good improvement.
I updated the example and also made a few other cosmetic changes to make it shiny and easy to read.

[nelson-liu]

this looks like a good change to me; in the future, please avoid squashing commits during development.

[amueller]

lgtm.