Add random fit scheduling algorithm.

Implement and add unit tests for naive scheduling algorithm. First filter the agents to match the container configuration and than just randomly choose one.

Constraints for now:

* cpu
* memory
* volumes
Fix schedule all task on one host
Merge pull request #63 from soundcloud/random-fit-algo

Random fit algo
Merge branch 'master' of github.com:soundcloud/harpoon into movecontainergen
Review changes. Works now.