stylesheet.css:
* remove unneeded !important
* fix inefficient rule
* don't hide aside in low resolutions
update version
stylesheet.css: fix section h1:before with small resolutions
Remove code and pre from normalize.css since stylesheet.css already has them.
Losslessly compress png files with https://github.com/subzey/zopfli-png.
update normalize.css
update js/pack.js with the latest uglify-js