Add first pass at width documentation.
Add first pass at width documentation.

topherauyeung/portfolio,pietgeursen/pietgeursen.github.io,topherauyeung/portfolio,tachyons-css/tachyons,fenderdigital/css-utilities,fenderdigital/css-utilities,cwonrails/tachyons,matyikriszta/moonlit-landing-page,topherauyeung/portfolio,getfrank/tachyons