Use util.debuglog instead of using different indidivudal styles for debugging

examples/eval.js

@@ -3,8 +3,6 @@
 var redis = require("../index"),
     client = redis.createClient();
 
-redis.debug_mode = true;
-
 client.eval("return 100.5", 0, function (err, res) {
     console.dir(err);
     console.dir(res);