Added the option to remove the meta and to customize the log message

I found the default logging to be very verbose. When a request is successful, I don't need to log all that data. So I just added new options: `options.meta = true/false` (to remove the meta object) and `options.msg` to customize the default logging message (using mustache like template)

e.g.

    server.use(expressWinston.logger({
      transports: [
        new winston.transports.Console({
            json: false
          , colorize: true
        }),
        new winston.transports.File({
            filename: "logs/access.log"
          , json: false
          , timestamp: true
        })
      ]
      , meta: false
      , msg: "{{res.statusCode}} {{req.method}} {{res.responseTime}}ms {{req.url}}"
    }));

Shows in the logs:

    info: 304 GET 8ms /about