Add global Logger object

New `Logger` object that can be setup once, then used throughout Cylon.

Usage:
```coffee-script
require './logger'
Logger.setup()

Logger.info "Informative message"
#=> "Informative message"
```

Defaults to writing to `console.log`. Can pass in a custom logger, or `false` which makes it use a no-op Logger class that won't print anything.