Swith to coreos/go-log from ccding/go-logging

bump(github.com/coreos/go-etcd): 57864cf81c66b8605816fafab3ab142e1c5f5b29
bump(github.com/coreos/go-log/log):
bump(github.com/coreos/go-systemd): 52f153170a52158deffce83502a9b6aed3744802
Switch from golang log to coreos/go-log
Fix nil logger in inits

Move the logger initialization out of init in util.go and into the
variable initializer.  This ensures that it will be run before any of
the other init functions.
Merge upstream
Merge pull request #187 from sakana/master

Switch to coreos/go-log