Handle multiple containers in the same pipeline

[richcooper95]

fixes #15

[richcooper95]

Not sure whether we should omit containers from the path, since the Pipeline directory doesn't have anything except the container directories inside - so we'd have this:

.
└── workflows
    └── promise
        └── configure
            ├── workflow.yaml
            └── pipeline-1
                  ├── another-testing-container
                  │   ├── ...
                  └── testing-container
                      ├── ...

Instead of this:

.
└── workflows
    └── promise
        └── configure
            ├── workflow.yaml
            └── pipeline-1
                ├── containers
                      ├── another-testing-container
                      │   ├── ...
                      └── testing-container
                          ├── ...

[richcooper95]

Opted for removing containers/!