update node-green to pass WCAG AA#536

Merged

silverwind merged 5 commits intonodejs:masterfrom

jrit:node-green

Mar 3, 2016

Commits on Feb 25, 2016

Commits on Mar 1, 2016

consolidating color use
jrit
committed

Commits on Mar 3, 2016

Merge branch 'master' of https://github.com/nodejs/nodejs.org into node-green
jrit
committed
make svg download logo visible on hover
jrit
committed