Revert "Make sure options are Hash"

This reverts commit 3a39544a98c58386e08e2df33a5db997baf34029.
When the options are loaded from a YAML file, it is originally loaded as `HashWithIndifferentAccess`
https://github.com/acl-services/message_queue/blob/master/lib/message_queue/rails.rb#L7
and the keys are strings. It will break when turned into a normal hash 
https://github.com/acl-services/message_queue/blob/master/lib/message_queue.rb#L78