Fix issue with radio choices styling

Introduced in 2f72a7b945c8a02b4592cd94a06f3d6f0a30fb5f
#2701: fix documentation inaccuracy
update 7-sidebars.md
update 10-custom-pages.md
update 11-decorators.md
update 12-arbre-components.md
add the IRC channel to the README
Update rspec to expect syntax, plus == to eq and improve rails version test inintegration/stylesheets_spec.rb plus split assets in spec/unit/asset_registration_space.rb