moved debug fn out to own module, added tests

lib/appenders/gelf.js

@@ -4,6 +4,7 @@ var layouts = require('../layouts');
 var levels = require('../levels');
 var dgram = require('dgram');
 var util = require('util');
+var debug = require('../debug')('GELF Appender');
 
 var LOG_EMERG=0;    // system is unusable
 var LOG_ALERT=1;    // action must be taken immediately
@@ -24,13 +25,6 @@ levelMapping[levels.WARN] = LOG_WARNING;
 levelMapping[levels.ERROR] = LOG_ERR;
 levelMapping[levels.FATAL] = LOG_CRIT;
 
-var debug;
-if (process.env.NODE_DEBUG && /\blog4js\b/.test(process.env.NODE_DEBUG)) {
-  debug = function(message) { console.error('LOG4JS: (GELF Appender) %s', message); };
-} else {
-  debug = function() { };
-}
-
 /**
  * GELF appender that supports sending UDP packets to a GELF compatible server such as Graylog
  *