Flatten attributes in attributes/default.rb

[bignastybryce]

Assigning attributes as hashes can cause some odd behavior during the merge. The attributes should be flattened to single values per assignment where possible. I know this takes a lot more typing, and I also know that I was the one who did it like this in the first place. I can only plead youth(!?) and ignorance. Might as well change the keys to strings instead of symbols while you're at it, to make foodcritic happy.