Try to detect an upgrade from Roadie 2 and explain it
Remove StyleProperties for a new StyleAttributeBuilder

The name was confusing and it was inefficiently implemented. The new
class have an intention-revealing name and has a much smaller
implementation.
Use a stable sort of properties emitted in style attributes

This should make sure that cases like the following are working
properly:

  h1 {
    background: red;
    background: rgba(255, 0, 0, 0.8);
  }
Release version 3.0! :cake: