add comment for migrating hierarchy

Thanks for providing such great examples!!!!

I tried to import terms with a hierarchy and ran into cryptic errors. The terms imported flat without the hierarchy.
After thinking about it it was obvious that I didn't import the parent terms first.
Adding another comment to line 102 of beer.inc would be helpful:

//make sure to import the parent terms first, see sort order above

A more "graceful" error handling would be another option.
thanks again