Rotation of log-files implemented. Closes #4
New log-file is created when size of the previous one reaches 512KB - timestamp is appended to the name of the file.
Closed log-file is automatically gzipped.
Logs older than 6 months are automatically deleted.
Merge branch 'rolling-log' into develop
Bumped version to v0.6
Merge branch 'release-0.6' into develop