Update phrasing and organization of code style guide

//cc @jagtalon @mattr555 @mwmiller

Thoughts?

I couldn't think of much/anything to add to the Perl right now but please feel free to lend suggestions or fill it in if you have something.

Regarding the JavaScript Structure part that I removed, I'm thinking it should be moved to the Spice code/design style guide, but perhaps it should just be on this page in a "Spice" section. I just felt it's not immediately important to the topic at hand which is a little more basic.
> Declare variables with `var`, chaining these like so is encouraged, with one line per variable:

Declare variables with `var`, chaining multiple declarations -- one per line: