Switch to glog for logging, bridge logging to glog.

1) imported glog to third_party (previous commit)
2) add support for third_party/update.sh to update just one pkg
3) search-and-replace:
  s/log.Printf/glog.Infof/
  s/log.Print/glog.Info/
  s/log.Fatalf/glog.Fatalf/
  s/log.Fatal/glog.Fatal/
4) convert glog.Info.*, err into glog.Error*

Adds some util interfaces to logging and calls them from each cmd, which
will set the default log output to write to glog.  Pass glog-wrapped
Loggers to etcd for logging.

Log files will go to /tmp - we should probably follow this up with a
default log dir for each cmd.

The glog lib is sort of weak in that it only flushes every 30 seconds, so
we spin up our own flushing goroutine.

third_party/deps.sh

@@ -1,6 +1,7 @@
 TOP_PACKAGES="
   github.com/coreos/go-etcd/etcd
   github.com/fsouza/go-dockerclient
+  github.com/golang/glog
   code.google.com/p/goauth2/compute/serviceaccount
   code.google.com/p/goauth2/oauth
   code.google.com/p/google-api-go-client/compute/v1

third_party/update.sh

@@ -13,6 +13,10 @@ cd $THIRD_PARTY_DIR
 
 . ./deps.sh
 
+if [ $# -gt 0 ]; then
+  PACKAGES="$@"
+fi
+
 # Create a temp GOPATH root.  It must be an absolute path
 mkdir -p ../output/go_dep_update
 cd ../output/go_dep_update