Fixed loading of Docker Compose volumes and networks.
Fixed loading of Docker Compose volumes and networks.

The yaml package won't decode key-only maps into map[string]struct{}, so
this commit switches back to using yaml.Node map values for the
intermediate loading representation in order to capture these keys. A
conversion function is used to ensure that yaml.Node types don't leak
into the package's API.

Signed-off-by: Jacob Howard <f862f167b85d41b225785c70d70808bc7337c1fe@havoc.io>

havoc-io/mutagen,havoc-io/mutagen