function hashString( str ) {
                var hash = 0,
                    i = 0,
                    len = str.length,
                    _char;
    
                for ( ; i < len; i++ ) {
                    _char = str.charCodeAt( i );
                    hash = _char + (hash << 6) + (hash << 16) - hash;
                }
    
                return hash;
            }
Appends a binary string.

@param {String} contents The binary string to be appended

@return {SparkMD5} The instance itself