Add play22.rb

In main play is replaced with typesafe-activator.
Adding play22.rb here since @leepa said it's still in heavy use.

See: https://github.com/Homebrew/homebrew/pull/30262#issuecomment-46581343
It does something when a `head` build is specified, but since we took out `head` the if will never be true, so this line can be removed.