Escaping characters in css selectors doesn't work
Created by: abotalov
Same bug as https://github.com/sparklemotion/nokogiri/pull/1303
Characters can be escaped in CSS selectors using backslashes - http://www.w3.org/TR/css3-selectors/#selector-syntax
From http://www.w3.org/TR/CSS21/syndata.html#characters:
Any character (except a hexadecimal digit, linefeed, carriage return, or form feed) can be escaped with a backslash to remove its special meaning. For example, """ is a string consisting of one double quote.
Third, backslash escapes allow authors to refer to characters they cannot easily put in a document. In this case, the backslash is followed by at most six hexadecimal digits (0..9A..F)