Removing specific attribution if I can't remember/list them all.

This commit is minor in the amount of lines changed, but I do want to document why it should change.

Firstly: read these tweets:
* https://twitter.com/juliepagano/statuses/439468105518297088
* https://twitter.com/juliepagano/statuses/439468219355910144
* https://twitter.com/juliepagano/statuses/439468290218676224

With that in mind:
* Jeff is far from the only source for our Code, but we did lift a lot from his gist for one of our paragraphs.
* I don't believe what Jeff offered is the equivalent to an acceptable Code.
* I certainly do appreciate the hard work of Ashe, Carina, Julie, etc - indeed, it was tweets from them (not to us, but to everyone) which prompted me to get the draft of this Code together.
* Listing only Jeff and not others in the sources is clearly problematic, and it's better to be more general rather than highlighting just the ones I clearly remember.

Given this isn't a change to the Code itself, I'm likely just to merge this anyway within the next day or so, given I do have commit rights. Our Code certainly has room to evolve - I make no claims of it being perfect - and perhaps those future changes could involve removing/rewording the paragraph that's linked to Jeff. I'd love to be a part of those discussions.

(And having written this, I've now seen #30. Sorry @lengarvey, I should have chimed in there. Given I was responsible for pulling the draft together - aided by work from @benschwarz - I feel personally responsible for this, so trying to fix things, one step at a time.)