v0.5.1: Bug-fix release

This is a bug-fix release on top of v0.5.0.

• Fix for dying with SIGALRM on OpenBSD (due to bug in Dasynq)
• Fix for signalling process group on OSes which don't allow getpgid() for processes in a different session
• Fix restarting of services which are started due to a dependent only
• Documentation updates and add contributed Getting Started guide