fix argument parsing (uptime and name got mixed up) and add a test

in commit https://github.com/Supervisor/superlance/commit/8603ce441c04a1b91b2e009e154bdccf552f3573 i mixed up the order of parameters in the init function resulting in the name being set to the uptime in seconds and the other way round.
factored out argument parsing into a separate method and added a test for it. hope this ensures mistakes like this one will be catched earlier next time ;-)