class Crass::Tokenizer

def valid_escape?(text = nil)

4.3.9. http://dev.w3.org/csswg/css-syntax/#starts-with-a-valid-escape

in the input stream will be checked, but will not be consumed.
valid escape sequence. If _text_ is `nil`, the current and next character
Returns `true` if the given two-character _text_ is the beginning of a 
def valid_escape?(text = nil)
  text = @s.current + @s.peek if text.nil?
  !!(text[0] == '\\' && text[1] != "\n")
end