Use better logger

[sebastienbarre]

Logging need some work. Consider:

• How to Get Node.js Logging Right
• sospedra/logatim: isomorphic logger which implements log levels and ANSI styles
• pimterry/loglevel: lightweight logging, adding log level methods to wrap console.log methods
• trentm/node-bunyan: simple and fast JSON logging module
• winstonjs/winston: multi-transport async logging library