Update README.md

[mbernier]

trafficstars

Fixed a couple link prefixes that were missing.

Links that don't exist anymore:

• - [HackerX](https://karangoel.typeform.com/to/mEl3P9) Goes to Typeform Main Page
• - [Spec](https://spec.fm/slack) 404 page
• https://scotch-slack.herokuapp.com/ "Nothing here yet message"
• - [Programming Bloggers](https://programmingbloggers.herokuapp.com/) "Nothing here yet message"

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