added gem5 at home

[Will-Shaddix]

I've only added 2 slides

1. links to github, slack, mailing lists, doxygen, youtube
2. slide mentioning performance characteristics of gem5, and that you ideally want a machine with lots of RAM and high single thread performance

I was planning on adding a 3rd with recommended practices but figured that was probably covered in contributing

Let me know if there's anything else i can add!