Replace deprecated function calls and resolve warnings.

[borderBite]

[NHDaly]

(Note also that i've pushed a commit to your branch to merge in master. Before editing anything, you'll want to do a git pull first to pull down that change. For more info on why I did that, please see the newly added https://github.com/JuliaComputing/JuliaBoxTutorials/blob/master/CONTRIBUTING.md 😁)

[NHDaly]

@logankilpatrick: I am going through my old PRs and noticed that we left this one unmerged. I'm not sure if there's been any changes to the repo since then, but would you be able to take this over and shepherd it through to merge? 🙏 thanks very much, and i'm sorry for the trouble!

Apologies @nslocum for the delay here!