Include environment in db:setup task

If railties (engines) contain migrations 'rake db:schema:load' imports all migrations in schema_migrations table, while 'rake db:setup' does not.

On the same project, which includes engines that have migrations on their own, running:

- rake db:schema:load produces:

```
mysql> select count(1) from schema_migrations;
+----------+
| count(1) |
+----------+
|      240 |
+----------+
```

- while rake db:setup produces:

```
mysql> select count(1) from schema_migrations;
+----------+
| count(1) |
+----------+
|      127 |
+----------+
```

The correct one is the first one, that includes all migrations. I can call db:create, db:schema:load and db:seed separately for now, but I'd like to use db:setup as one command only is always better than three.

I'd be happy to add a test case if possible.