Remove baseInterfaceSpec
Remove baseInterfaceSpec

- Remove String() from interfaceSpec
- Put Spec in each implementation struct
- parseInterfaceSpec can now return nil on error

joyent/containerbuddy,justenwalker/containerbuddy,tgross/containerbuddy,justenwalker/containerpilot,justenwalker/containerbuddy,flyinprogrammer/containerpilot,benoittoulme/containerpilot,flyinprogrammer/containerpilot,joyent/containerpilot,justenwalker/containerpilot,benoittoulme/containerpilot,joyent/containerbuddy,joyent/containerpilot,benoittoulme/containerpilot,joyent/containerpilot,tgross/containerbuddy