We need to include models we use

Probably some left over L5 migration stuff, since you wouldn't notice it until reversing a migration

database/migrations/2014_12_13_190730_changes_for_v321.php

@@ -1,5 +1,7 @@
 <?php
 
+use FireflyIII\Models\Budget;
+use FireflyIII\Models\Category;
 use FireflyIII\Models\BudgetLimit;
 use FireflyIII\Models\Component;
 use Illuminate\Database\Migrations\Migration;