cleanup: Remove `puts` from tests
Global logger for combi
Control with env:
- LOG_LEVEL=NONE|ERROR|WARN|INFO|DEBUG
- DEBUG=true  --> DEBUG (backwards compat)
- default is INFO
- logs to STDOUT with default format (includes timestamp, pid, log level and message) http://www.ruby-doc.org/stdlib-2.1.1/libdoc/logger/rdoc/Logger.html#class-Logger-label-Format