v2

- Prevent double-close panic in conn.Close
- Fix flaky tests: don't rely on map iteration order.
- go vet: fix raw struct initialization
- worker: don't drop signals
- Add UnixCredentials system call for DragonFly BSD
- XML doctype declaration for introspection
- decouple connections from unixTransport
Merge pull request #13 from bcwaldon/contributing

Add CONTRIBUTING.md and MAINTAINERS