fixed scoping of validation

lib/dao-factory.js

@@ -675,16 +675,23 @@ module.exports = (function() {
 
     return new Utils.CustomEventEmitter(function(emitter) {
       if (options.validate === true) {
-        this.build(attrValueHash).validate().success(function(errors) {
-          if (!!errors) {
-            emitter.emit('error', errors)
-          } else {
-            this
-              .QueryInterface
-              .bulkUpdate(this.tableName, attrValueHash, where, options)
-              .proxy(emitter)
-          }
-        }.bind(this))
+        var build    = this.build(attrValueHash)
+          , attrKeys = Object.keys(attrValueHash)
+
+        build
+          .validate({
+            skip: Object.keys(build.dataValues).filter(function(val) { return attrKeys.indexOf(val) !== -1 })
+          })
+          .success(function(errors) {
+            if (!!errors) {
+              emitter.emit('error', errors)
+            } else {
+              this
+                .QueryInterface
+                .bulkUpdate(this.tableName, attrValueHash, where, options)
+                .proxy(emitter)
+            }
+          }.bind(this))
       } else {
         this
           .QueryInterface