_.base64encode = function(string) {
        var padding = '=',
            chrTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' +
                '0123456789+/';

        function utf8Encode(str) {
            var bytes = [], offset = 0, length, char;

            str = encodeURI(str);
            length = str.length;

            while (offset < length) {
                char = str[offset];
                offset += 1;

                if ('%' !== char) {
                    bytes.push(char.charCodeAt(0));
                } else {
                    char = str[offset] + str[offset + 1];
                    bytes.push(parseInt(char, 16));
                    offset += 2;
                }
            }

            return bytes;
        }


        var result = '',
            bytes = utf8Encode(string),
            length = bytes.length,
            i;

        // Convert every three bytes to 4 ascii characters.
        for (i = 0; i < (length - 2); i += 3) {
            result += chrTable[bytes[i] >> 2];
            result += chrTable[((bytes[i] & 0x03) << 4) + (bytes[i+1] >> 4)];
            result += chrTable[((bytes[i+1] & 0x0f) << 2) + (bytes[i+2] >> 6)];
            result += chrTable[bytes[i+2] & 0x3f];
        }

        // Convert the remaining 1 or 2 bytes, pad out to 4 characters.
        if (length%3) {
            i = length - (length%3);
            result += chrTable[bytes[i] >> 2];
            if ((length%3) === 2) {
                result += chrTable[((bytes[i] & 0x03) << 4) + (bytes[i+1] >> 4)];
                result += chrTable[(bytes[i+1] & 0x0f) << 2];
                result += padding;
            } else {
                result += chrTable[(bytes[i] & 0x03) << 4];
                result += padding + padding;
            }
        }

        return result;
    };