Replace HashiCorp use case with PuTTY

[MattTheCuber]

Closes #71 and closes #77

HashiCorp's ZeroVer reign is so 0ver.

Instead of just updated the use case, I thought I would replace it with a better example. Let me know if this isn't a good idea. Also, feel free to provide suggestions to the wording or add/remove something.

[mahmoud]

A good start! I punched up the language a bit, but on the note of "punching up" I should say (at the risk of breaking character lol): We probably want to keep the Hashicorp case study, if only in the past tense. Why?

• It's system infrastructure (not user-facing)
• It's for-profit (sufficient resources for maintenance)
• Hashicorp is a large org with marketing and devrel people that should know better

Ideally 0ver's tongue-in-cheek admonishment would influence well-resourced orgs selling a product to communicate more honestly about their project status. We're trying to punch up.

To my knowledge, PuTTY isn't really resourced, and it's 90%+ still just Simon. I know what I'd do in their position (rip off the bandaid and use a real version), I'm ambivalent about putting smaller devs on blast, and definitely want to keep as many big orgs on notice as possible.