Remove all global log invocations

[peterbourgon]

Fixes #21

[rade]

Is putting a logger field into most structs, and adding an extra arg to the initialisation methods really the best way to go about this?

Most things have access to router.Ourself, so could just use the logger in that.

Though ironically with my changes in #33 and the changes in here, I think LocalPeer isn't actually doing any logging itself anymore - it only needs a logger in order to feed it into the LocalConnection constructor.

[peterbourgon]

I elected to make the minimum changes necessary. I am happy to refactor further. May I delete methods like remoteConnection.log, or is that prefix useful/necessary?

[rade]

#33 gets rid of remoteConnection.log.

[bboreham]

It would be easier to integrate this with other schemes if it took an interface rather than a concrete *log.Logger.

[peterbourgon]

Agreed. #37