Introduce logging framework/library

[Eskibear]

The vanilla console.log/warn/error is convenient, and works on both client-side (browser) and server-side(e.g. nodejs) apps. But it only prints to stdout/stderr.

Popular logging frameworks like winston is powerful, providing different log levels, different format of output (stdout, a file, and a database etc.). But is not directly working on client-side so far, and introduce more dependencies.

A feasible solution is using a customized logger, and delegate logger.log to console.log or winston based on running environment.