Scheduling fixed

Using the module, an error pop up in the worker:

    2014-01-25T19:25:01Z 40935 TID-zq5lo4 ERROR: ERR value is not a valid float
    2014-01-25T19:25:01Z 40935 TID-zq5lo4 ERROR: /Users/jam/.rvm/gems/ruby-2.1.0/gems/redis-3.0.7/lib/redis/client.rb:97:in `call'

After doing some tests, sidekiq needs the date in epoch, so I changed it.

Thanks for this useful module!