Add schedules tab configuration procedure in README

[aclarembeau]

Hello,

I struggled a bit of time to see that my schedules where not showing in the schedules tab of resque-scheduler-web.

According to:
resque/resque-scheduler#541

What I had to do is just to create an initializer:
Resque.schedule = YAML.load_file Rails.root.join('schedules.yml')

Instead of creating a rake task, as advertised in https://github.com/resque/resque-scheduler
As I believe that many other users will have the issue, I purpose to add this to the readme.

Thanks a lot for the amazing job team.
Resque, with the help of resque-web is definitely one of the easiest queuing backend for rails thanks to your awesome work :)