v0.2.0 Pre-alpha release

This is a feature release, still considered pre-alpha but with no major known bugs.

• now loads services from multiple directories: /etc/dinit.d, /usr/local/lib/dinit.d, and /lib/dinit.d
• control socket path and /sbin directory (used to find shutdown) can be configured at build time
• option to substitute environment variables in service command lines (load-options = sub-vars)
• several bugfixes.