Auto generated client for the signer service.

The service is implemented using Cloud Endpoints
https://cloud.google.com/endpoints/

The signer-api.json file is auto generated from the server implementation.

The signer-gen.go file is generated using
google.golang.org/api/google-api-go-generator:

google-api-go-generator --api_json_file=signer-api.json -output=signer-gen.go