Minor style inconsistencies between crates.io and doc.crates.io

[birkenfeld]

(Not sure this belongs here or in the cargo repo.)

While adding the docs header link to crates.io for #267, I noticed several differences in the stylesheet.

• The default font-face is different: doc.crates.io only specifies sans-serif, while crates.io specifies "Helvetica Neue",...,sans-serif.
• The dropdown menu "buttons" at the top (Documentation for doc.crates.io, the user menu for crates.io) are styled differently when the menu is open: only doc.crates.io makes the button look depressed and reverses the arrow direction.

[steveklabnik]

I'm not sure either, but synchronizing them would be good, probably.

[carols10cents]

I'm closing this since the cargo docs are about to be rendered completely differently using mdbook :)