Resque::Failure::Multiple calls save to all backends even if some backends fail

[labocho]

When some failure backend raise error during Resque::Failure::Multiple#save, the rest backends' save are never called.

class BrokenBackend < Resque::Failure::Base
  def save
    raise "Broken"
  end
end

Resque::Failure::Multiple.classes = [BrokenBackend, Resque::Failure::Redis]
Resque::Failure.backend = Resque::Failure::Multiple

# When a job fails, Resque::Failure::Redis#save is never called.

I want to call all backends' save for redundancy. I wrote patch to call all backends and wrap original error(s).

[matthewhively]

This would be cool if this could be fixed up and merged in.