fix blank bulkCreates in postgres

lib/dialects/postgres/query-generator.js

@@ -295,11 +295,24 @@ module.exports = (function() {
     bulkInsertQuery: function(tableName, attrValueHashes) {
       var query     = "INSERT INTO <%= table %> (<%= attributes %>) VALUES <%= tuples %> RETURNING *;"
         , tuples    = []
+        , serials   = []
+
+      Utils._.forEach(attrValueHashes, function(attrValueHash, i) {
+        if (i === 0) {
+          Utils._.forEach(attrValueHash, function(value, key, hash) {
+            if (tables[tableName] && tables[tableName][key]) {
+              if (['bigserial', 'serial'].indexOf(tables[tableName][key]) !== -1) {
+                serials.push(key)
+              }
+            }
+          })
+        }
 
-      Utils._.forEach(attrValueHashes, function(attrValueHash) {
-        removeSerialsFromHash(tableName, attrValueHash)
         tuples.push("(" +
-          Utils._.values(attrValueHash).map(function(value){
+          Utils._.map(attrValueHash, function(value, key){
+            if (serials.indexOf(key) !== -1) {
+              return 'DEFAULT';
+            }
             return this.escape(value)
           }.bind(this)).join(",") +
         ")")

test/associations/has-many.test.js

@@ -915,6 +915,8 @@ describe(Support.getTestDialectTeaser("HasMany"), function() {
                     })
                   })
                 })
+              }).on('sql', function (sql) {
+                console.log(sql)
               })
             })
           })

test/dao-factory/create.test.js

@@ -883,6 +883,17 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
       })
     })
 
+    it('should allow blank creates (with timestamps: false)', function (done) {
+      var Worker = this.sequelize.define('Worker', {}, {timestamps: false})
+      Worker.sync().done(function(err) { 
+        Worker.bulkCreate([{}, {}]).done(function (err, workers) {
+          expect(err).not.to.be.ok
+          expect(workers).to.be.ok
+          done()
+        })
+      })
+    })
+
     describe('enums', function() {
       it('correctly restores enum values', function(done) {
         var self = this