code: function compareSpecificity(selectorA, selectorB) {
      return selectorA.attributeCount - selectorB.attributeCount ||
          selectorA.identifierCount - selectorB.identifierCount ||
          (selectorA.rawSelector <= selectorB.rawSelector ? -1 : 1);
  }
docs: Compares the specificity of two selector objects, with CSS-like rules.
  @param {ASTSelector} selectorA An AST selector descriptor
  @param {ASTSelector} selectorB Another AST selector descriptor
  @returns {number}
  a value less than 0 if selectorA is less specific than selectorB
  a value greater than 0 if selectorA is more specific than selectorB
  a value less than 0 if selectorA and selectorB have the same specificity, and selectorA <= selectorB alphabetically
  a value greater than 0 if selectorA and selectorB have the same specificity, and selectorA > selectorB alphabetically