Update readme to reflect changes made in PR #141.
Update readme to reflect changes made in PR #141.

After PR #141 the the `backend_service` cloud_property takes either
a string or a Map of strings, allowing the creation of a
Internal Load Balancer.

evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release