Use Knapsack to evenly distribute specs
This merges support for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4240 and is based on: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/442
This merges support for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4240 and is based on: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/442