chore(package): update postcss-cssnext to version 3.0.2
chore(package): update postcss-cssnext to version 3.0.2

Closes #344
ciscospark/react-ciscospark,ciscospark/react-ciscospark,ciscospark/react-ciscospark,adamweeks/react-ciscospark-1,adamweeks/react-ciscospark-1,adamweeks/react-ciscospark-1