articles: use they/them for pronoun to be in sync with current pronoun war

See here:
 https://github.com/joyent/libuv/pull/1015
 https://en.wikipedia.org/wiki/Singular_they
less: use variables in @media

This is now something allowed.
css: wider code blocks

This is an intrusive change since we have to compute margins in inner
elements inside of specifying them in the outer elements. Code blocks
can now span the entire page, as well as images.
css: restore margins for lists

This seems better-looking than using existing margins for
numbers/bullets.
css: restore margins in resume css