Add Weighted Round Robin Algorithm

[sp1thas]

Hi there,
Fist of all congrats for your project. I'm using cronicle in production and I'm very satisfied of it's stability.

I would like to propose an enchantment. When you select a target group, you have the ability to choose round robin algorithm which is a good option when you have slaves with similar resources. The problem is that round robin is not working very well when slaves are different in terms of resources.

Weighted Round Robin Algorithm could solve the problem and optimize utilization.

I know that you are not working full-time on Cronicle and it's totally understandable, therefore consider this issue as an idea for a future version.