better option definition

lib/dialects/mysql/query-generator.js

@@ -4,7 +4,10 @@ var Utils = require("../../utils")
 module.exports = (function() {
   var QueryGenerator = {
     createTableQuery: function(tableName, attributes, options) {
-      options = options || {}
+      options = Utils._.extend({
+        engine: 'InnoDB',
+        charset: null
+      }, options || {})
 
       var query   = "CREATE TABLE IF NOT EXISTS <%= table %> (<%= attributes%>) ENGINE=<%= engine %> <%= charset %>"
         , primaryKeys = []
@@ -20,7 +23,7 @@ module.exports = (function() {
         , values  = {
             table: Utils.addTicks(tableName),
             attributes: attrStr,
-            engine: options.engine || 'InnoDB',
+            engine: options.engine,
             charset: (options.charset ? "DEFAULT CHARSET=" + options.charset : "")
           }
         , pkString = primaryKeys.map(function(pk) {return Utils.addTicks(pk)}).join(", ")