Guide: intro edits

This is mostly organizational and simplifying. However, I also removed prose which I took to be too basic given that we expect this to be read by programmers. Comments welcome.

cc @steveklabnik 
I am agreeing that `>`s are used incorrectly here.

> If it's wrong here, then the other instances need to change as well. 

Yes, I can't remember that being used, though I could pretty easily go check it out.