Add more git resources

[ndanielsen]

https://pbs.twimg.com/media/DJAqiD9UwAAVOtb.jpg

[ndanielsen]

http://eagain.net/articles/git-for-computer-scientists/

[ndanielsen]

Source for git twitter image:
https://twitter.com/girlie_mac/status/1044044900755369984

[capsulecorplab]

This may be relevant/useful
http://think-like-a-git.net/