rds: make hash policy extensible. (#52)
rds: make hash policy extensible. (#52)

Fixes #5.

jrajahalme/envoy-api,jrajahalme/envoy-api,rshriram/envoy-api,rshriram/envoy-api,lyft/envoy-api,lyft/envoy-api,lyft/envoy-api,jrajahalme/envoy-api,jrajahalme/envoy-api,rshriram/envoy-api