feat: option to disable legend

[boonware]

Issue

#19

Description

• Add a new parameter to each visualization function to disable showing the legend in plots. Defaults to True.
• Style changes were made via tox -e style.

@BryceFuller

[CLAassistant]

All committers have signed the CLA.

[mrossinek]

Please also add a release note which highlights the addition of the show_legend keyword argument to the various visualization functions.

We are still missing the section describing this in our CONTRIBUTING.md guide, but you can have a look here for how that is done.

[boonware]

@mrossinek Requested changes have been made:

1. Updated param to be keyword-only.
2. Added a release note.

[boonware]

@mrossinek Can I get another review on this one? Thanks

[coveralls]

Pull Request Test Coverage Report for Build 11681029072

Details

• 15 of 15 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 11554634560:	0.0%
Covered Lines:	431
Relevant Lines:	431

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💛 - Coveralls

[boonware]

@mrossinek The test case test_backpropagate_timeout is failing. Judging by the name, and the test code, I suspect this is down to a test instability and not related to my changes, which appear unrelated to the test case. Can we run the suite again?