Fix #97 unref() the rotation timeout in RotatingFileStream.

The rotation `setTimeout` from `RotatingFileStream` will prevent the process from exiting.
This fix simply `unref()` the timeout immediately after it is set.
Graceful termination failing test for #97 and #73

Will fail if any timers or callbacks remain registered when
instantiating a logger with a rotating file.
Merge 'chakrit/master' fixing #97 process not exiting
Changelog for 'unref' bugfix #97