In item page, display human bytes of file size.
In item index page, if product's description isn't blank, display it.
In item page, if product's description isn't blank, display it for item's description.
app/views/items/index_not_signed_in.html.erb: Japanize.
app/views/items/show_not_signed_in.html.erb: Japanize.
app/views/products/show_not_owner.html.erb: Japanize.
app/views/brands/show_not_owner.html.erb: Japanize.
app/views/brands/index.html.erb: Japanize.
app/views/products/index.html.erb: Japanize.
app/views/layouts/application.html.erb: Japanize.
Merge branch 'japanize'