Change dummy pid to avoid killing real processes
Stub process killing
Enhance specs for worker killing
Fix dummy PID in specs
Minor refactoring
Fix specs
Don't expect error class anymore;

this is deprecated
Fail if worker pid could not be saved;

We have to ensure this because if saving fails,
it may lead to infinite spawning of workers.
Minor refactoring
Exit stalled worker autonomously
Don't allow a message for #halt anymore;

it has not been processed anyway
Get fresh worker before controlling it
Update status only if it changed
Version 2.0.2
Fix specs
Stop worker context-sensitively