v3

- Add BusObject interface
- Add ExportSubtree functions for subtree support
- Add ExportWithMap method to support exporting
  lower-case method names
- Fix mutex unlocking when releasing object
- Fix encoder alignment
- Fix nil dereference
- Used NameAcquired/NameLost signals to track names
Merge pull request #42 from QuentinPerez/patch1

Fix nil dereference