Add .mailmap file, add programmer humor

[heptocat]

@laurendc I honestly don't really know what we would need a .mailmap file for here, but also, I'm inexperienced with these things. Maybe @DarthFloopy can explain why they think it'd be good to have?

[josephcagle]

I use different email addresses for my GitHub account and my Git email address, so I add lines in a .mailmap file to tell e.g. git log to show both addresses as belonging to me (for whenever I do things through github.com instead of Git). Hopefully that makes sense ... :)

[heptocat]

Thanks for clearing that up @DarthFloopy . But I understand that means it does not need to be on our repository. I will delete it and then merge.