Removing sections regarding selector performance

Some very smart people argue CSS selector performance really doesn't matter any longer. I'm inclined to agree.

http://benfrain.com/css-performance-revisited-selectors-bloat-expensive-styles/
http://calendar.perfplanet.com/2011/css-selector-performance-has-changed-for-the-better/

The latter is from 2011 and things have gotten even better since then. Yes, classes and ids are still very marginally better than anything else, but as we advocate SMACSS/BEM-style short, class-based selectors anyhow, I'd say that when we don't, it doesn't really matter. It's not like we're styling entire sites based off div div + span:nth-child(3n+6) *.

(And if we are, we have bigger problems ;) ).