kubernetes or openshift does not allow underscores in the object
names, while docker-compose does, in this commit the code has been
added to convert underscores to hypens.
This adds support for supplying for example:
"127.0.0.1:80:80/tcp" to docker-compose.yaml and converting it to it's
corresponding Kubernetes / OpenShift hostIP.
This commit also refactors the loadPorts function of compose.go
Closes https://github.com/kubernetes-incubator/kompose/issues/335
Moved label handling code from Transformer to loader,
to make it generic to handle creating service types.
Added new attribute to ServiceConfig which gets populated
in loader.
Fixes#273
