修复seeder错误；删除第三方的think迁移工具，在extend中重新实现；

extend/think/migration/command/stubs/migrate.stub

@@ -0,0 +1,33 @@
+<?php
+
+use think\migration\Migrator;
+use think\migration\db\Column;
+
+class MigratorClass extends Migrator
+{
+    /**
+     * Change Method.
+     *
+     * Write your reversible migrations using this method.
+     *
+     * More information on writing migrations is available here:
+     * http://docs.phinx.org/en/latest/migrations.html#the-abstractmigration-class
+     *
+     * The following commands can be used in this method and Phinx will
+     * automatically reverse them when rolling back:
+     *
+     *    createTable
+     *    renameTable
+     *    addColumn
+     *    renameColumn
+     *    addIndex
+     *    addForeignKey
+     *
+     * Remember to call "create()" or "update()" and NOT "save()" when working
+     * with the Table class.
+     */
+    public function change()
+    {
+
+    }
+}