class Roadie::Selector

We cannot inline styles that appear inside "@" constructs, like +@keyframes+.

(like +::placeholder+, +::before+) or a pseudo function (like +:active+).
It's impossible to inline properties that applies to a pseudo element
Returns whenever or not a selector can be inlined.

def inlinable?
  !(pseudo_element? || at_rule? || pseudo_function?)
end