Corrects CC API endpoint for create-service command

- create-service should retrieve the list of services and plans  from
  /v2/spaces/:guid/services instead of /v2/services. This ensures that
  the plans used to create the instance are visible for the requesting
  user.
Merge pull request #92 from cloudfoundry/create_only_visible_plans

Corrects CC API endpoint for create-service command