skipString = function () {
								var quote = content.charAt(pos);
								if (quote == '"' || quote == "'") {
									while (--pos >= 0) {
										if (content.charAt(pos) == quote && content.charAt(pos - 1) != '\\') {
											break;
										}
									}
									return true;
								}

								return false;
							}
Extracts CSS selector from CSS document from
given position. The selector is located by moving backward
from given position which means that passed position
must point to the end of selector 
@param  {String}  content CSS source
@param  {Number}  pos     Search position
@param  {Boolean} sanitize Sanitize CSS source before processing.
Off by default and assumes that CSS must be comment-free already
(for performance)
@return {Range}