Issue 239: Cleanup Rake Tasks

Follow up to https://github.com/MarkUsProject/Markus/pull/1156
In relation to https://github.com/MarkUsProject/Markus/issues/239
Merged master.

Fixed lib/tasks/simulator.rake. The name generation was being done in such a way that you'd end up with conflicts. So I changed the naming scheme. And Mark.mark needs to be in a range of 0..4, so m.mark = rand(criterion.weight) would cause errors since criterion weights can vary.