Added logic to serialize Error objects correctly

This should fix #97.

lib/appenders/clustered.js

@@ -7,6 +7,14 @@ var log4js = require('../log4js');
  * Takes a loggingEvent object, returns string representation of it.
  */
 function serializeLoggingEvent(loggingEvent) {
+	// JSON.stringify(new Error('test')) returns {}, which is not really useful for us.
+	// The following allows us to serialize errors correctly.
+	for (var i = 0; i < loggingEvent.data.length; i++) {
+		var item = loggingEvent.data[i];
+		if (item && item.stack && JSON.stringify(item) === '{}') { // Validate that we really are in this case
+			loggingEvent.data[i] = {stack : item.stack};
+		}
+	}
 	return JSON.stringify(loggingEvent);
 }
 
@@ -115,4 +123,4 @@ function configure(config, options) {
 }
 
 exports.appender = createAppender;
-exports.configure = configure; 
+exports.configure = configure; 

lib/appenders/multiprocess.js

@@ -94,6 +94,11 @@ function workerAppender(config) {
   }
   
   function write(loggingEvent) {
+	// JSON.stringify(new Error('test')) returns {}, which is not really useful for us.
+	// The following allows us to serialize errors correctly.
+	if (loggingEvent && loggingEvent.stack && JSON.stringify(loggingEvent) === '{}') { // Validate that we really are in this case
+		loggingEvent = {stack : loggingEvent.stack};
+	}
     socket.write(JSON.stringify(loggingEvent), 'utf8');
     socket.write(END_MSG, 'utf8');
   }