Remove Entrypoint from Kompose object

We had Command and Args together with Entrypoint in Kompose object.
This doesn't make much sense, as Entrypoint and Command are same thing.
I've removed Entrypoint from Kompose object in favor of Command to keep
same naming convensions as in Kubernetes.

Entrypoint from docker-compose.yml is now saved to Command and Command
is saved to Args (http://kubernetes.io/docs/user-guide/containers/).

docker-compose.yml | Kompose object
-------------------|---------------
  Entrypoint       |    Command
   Command         |     Args

pkg/kobject/kobject.go

@@ -145,7 +145,6 @@ type ServiceConfig struct {
 	CPUQuota      int64
 	CapAdd        []string
 	CapDrop       []string
-	Entrypoint    []string
 	Expose        []string
 	Privileged    bool
 	Restart       string