Library to implement a well-behaved Unix daemon process.

This library implements the well-behaved daemon specification of PEP 3143,
"Standard daemon process library".

A well-behaved Unix daemon process is tricky to get right, but the required
steps are much the same for every daemon program. A DaemonContext instance holds
the behaviour and configured process environment for the program; use the
instance as a context manager to enter a daemon state.
