adapt migrations files to flex

migrations/Version20160318111334.php

@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -13,7 +13,7 @@ class Version20160318111334 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function up(Schema $schema)
+    public function up(Schema $schema): void
     {
         // this up() migration is auto-generated, please modify it to your needs
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
@@ -109,7 +109,7 @@ class Version20160318111334 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function down(Schema $schema)
+    public function down(Schema $schema): void
     {
         // this down() migration is auto-generated, please modify it to your needs
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');