refactoring and commenting rating microservice
refactoring and commenting rating microservice

add comments to all API methods.
refactor use of environment variables.
change HTTP verb for recollect() from GET to PUT to reflect that
the function changes data. PATCH verb cannot be used since it isn't
supported by scheduler or AppEngine cron jobs.

GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox