Prefer Ruby style for single word collections

According to the Ruby style guide, %w{} collections for arrays of single
words are preferred. They're easier to type, and if you want a quick
grep, they're easier to search.

This change converts all Payloads to this format if there is more than
one payload to choose from.

It also alphabetizes the payloads, so the order can be more predictable,
and for long sets, easier to scan with eyeballs.

See:
  https://github.com/bbatsov/ruby-style-guide#collections