added option storeHost, if it is set to true adds 'hostname' field to mongodb entry with os.hostname()

lib/winston-mongodb.js

@@ -7,6 +7,7 @@
  */
 
 var util = require('util');
+var os = require('os');
 var mongodb = require('mongodb');
 var winston = require('winston');
 var common = require('winston/lib/winston/common');
@@ -39,6 +40,7 @@ var MongoDB = exports.MongoDB = function (options) {
   this.capped       = options.capped;
   this.cappedSize   = options.cappedSize || 10000000;
   this.nativeParser = options.nativeParser || false;
+  this.storeHost    = options.storeHost;
   // TODO: possibly go by docs (`max`) instead
   // this.length       = options.length    || 200;
 
@@ -140,6 +142,9 @@ MongoDB.prototype.log = function (level, msg, meta, callback) {
         entry.timestamp = new Date;
         entry.level = level;
         entry.message = msg;
+        if (self.storeHost) {
+          entry.hostname = os.hostname();
+        }
 
         col.save(entry, { safe: self.safe }, function (err) {
           if (err) {