v1.15.4

• dedupe modules with same hash when computing graph. (#619)
• prevent memory usage burst when writing mapper by streaming protobuf items to writer
• ignore "service currently overloaded" worker errors in the "maxRetries" count. Tier1 requests should not error out because tier2 servers are ramping up, only when they fail multiple times.
• Default SUBSTREAMS_WORKER_MAX_RETRIES now set to 5.