Option retry_policy is dismissed on start_workflow.

I was trying to set a retry policy by passing a `retry_policy` hash in the `options` hash when calling `start_workflow` but it didn't work.
I went digging in the code and realized it is indeed omitted: even if the execution options are built with the policy, they are not used on the underlying call to `start_workflow_execution` at https://github.com/coinbase/temporal-ruby/blob/master/lib/temporal/client.rb#L43.

The only way I was able to actually set a policy was by calling `retry_policy` in an activity, but that leaves the caller powerless on setting a retry policy, and it seems it doesn't apply to workflows either.

Is this a regression? Was it always a bug? The readme states you can pass this option.