Logging and connection fixes.

* Add support for setting logging levels
* Re-use the same Etcd client instead of instantiaing a new one every reload
I see. I noticed that you run plain `go install` in the [Makefile](https://github.com/mailgun/vulcand/blob/master/Makefile#L50) - does the `GOPATH` get set to this `_workspace` directory automatically?