Update installation instructions

darcs-hash:20100626072822-58252-ce5ff6b6ff4e3b5ddb8675eb8302eaf21ae08ef6
Don't enable bonjour account if bonjour support is not detected

Ignore-this: 69900ec1890cd9f9b9ef7f78cfb4d99b

Also added 'available' property, indicating bonjour support

darcs-hash:20100629123324-56b4d-d5acbff6e503fd07bc038601a2b694097c6d9523