Logging

A common interface for task logging/events.

• debug(message)
• info(message)
• warn(message)
• error(message)
• fatal(message)

Debug messages should only be respected when the task is in verbose mode. All messages should be suppressed in silent mode.

@thanpolas > I've done some work for node-logg, it can be easily manipulated to fit all requirements as it emits events in various facets (per logger hierarchy, log level).