docs: function stringToRegexp (path, keys, options) {
  	  var tokens = parse(path)
  	  var re = tokensToRegExp(tokens, options)
  	
  	  // Attach keys back to the regexp.
  	  for (var i = 0; i < tokens.length; i++) {
  	    if (typeof tokens[i] !== 'string') {
  	      keys.push(tokens[i])
  	    }
  	  }
  	
  	  return attachKeys(re, keys)
  	}