Possible solution for contributor issue.

This is a tentative solution for #40, it gives credit to people like @wei2912, @beingbrown, @tangentstorm, and @DTSCode, who have been incredibly helpful, but haven't submitted new text to the book. For the latter reason, listing them as "authors" would be misleading. Instead, I want to list y'all as "noted contributors".

It's a silly pedantic issue, but it nonetheless bothers me.

Thanks!