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.
>  Mixing code changes with indentation fixes makes for git diffs that are difficult to read.

"It is important that reviewers be able to differentiate between functional and stylistic changes."

That's not so great, either, but I don't much like "git diff"