title, abstract, intro

[davidwhogg]

I just refactored the abstract and it needs checking. I edited in the browser, so I may have broken LaTeX. I made huge changes to the ordering, to get it into context, aims, method, results order. I explicitly called out the differences with Petigura, which I now think is necessary.

I only tweaked the Intro. Let me know when you need more. Signed, @davidwhogg

[dfm]

Looks good to me. I'll probably remove some of your semi-colons eventually.