title: Is migration always needed?
body: <p>Right now my code in AppDelegate.m is:</p>
  
  <pre><code>[MagicalRecord setupAutoMigratingCoreDataStack];
  [MagicalRecord setupCoreDataStackWithAutoMigratingSqliteStoreNamed:@"db.sqlite"];
  </code></pre>
  
  <p>Does it cost much? Does any code exist like:</p>
  
  <pre><code>if (DB.version == newVersion) {
      [MagicalRecord setupAutoMigratingCoreDataStack];
      [MagicalRecord setupCoreDataStackWithAutoMigratingSqliteStoreNamed:@"db.sqlite"];
  }
  else {
      [MagicalRecord setupCoreDataStack];
      [MagicalRecord setupCoreDataStackWithStoreNamed:@"db.sqlite"];
  }
  </code></pre>
  
  <p>that would save some performance instead of force-migrating every time? Or does MagicalRecord/CoreData handle this if statement internally?</p>