v1.5.1

Small hotfix release (Do not fill the disk)

fixes #213: bumblebee-status always logged messages to stderr (even when -d was not specified), which end up in ~/.xsession-errors and consume a lot of diskspace very quickly.

This release completely disables logging, as long as -d is not specified.

Also, introduces two "special" log file names, stdout and stderr to log to stdout and stderr, respectively.