Adding prettyPrint parameter as function example.

examples/custom-pretty-print.js

@@ -0,0 +1,18 @@
+var winston = require('../lib/winston');
+
+function myPrettyPrint(obj) {
+  return JSON.stringify(obj)
+    .replace(/\{/g, '< wow ')
+    .replace(/\:/g, ' such ')
+    .replace(/\}/g, ' >');
+}
+
+var logger = new (winston.Logger)({
+  transports: [
+    new (winston.transports.Console)({ prettyPrint: myPrettyPrint }),
+  ]
+});
+
+logger.info('Hello, this is a logging event with a custom pretty print',  { 'foo': 'bar' });
+logger.info('Hello, this is a logging event with a custom pretty print2', { 'foo': 'bar' });
+