Run() should return channel of image messages

[taotetek]

When starting the service, the Run() command should return a channel of *RevisitMsg 's. This way, messages passing through a service can also be mirrored to a stream for other purposes.

This would allow building services that do things like post to an image hosting service without having to access the internal logic of the post handler.

[taotetek]

Instead, I think I'll make a separate RunWithChannel() function so as to not add complexity to making a simple service.

[taotetek]

closing this for now - not needed due to change of plans