Agent - 0.4.0

## [0.4.0] - October 23rd, 2019
- Adds admin endpoints for health, info and metrics
- Adds requestId to logs and response header
- Improves log integration with Optimizely SDK
- Updates swagger spec to match current server implementation
- Updates dependency version for the Optimizely SDK
- Enhance webhook service configurability

https://github.com/optimizely/agent/releases/tag/v0.4.0