message: docs: add changelog for 5.1.0-rc.1
diff: +<a name="5.1.0-rc.1"></a>
  +# [5.1.0-rc.1](https://github.com/angular/angular/compare/5.1.0-rc.0...5.1.0-rc.1) (2017-12-01)
  +
  +
  +### Bug Fixes
  +
  +* **compiler-cli:** propagate ts.SourceFile moduleName into metadata ([f841fbe](https://github.com/angular/angular/commit/f841fbe))
  +* **service-worker:** allow disabling SW while still using services ([65f4fad](https://github.com/angular/angular/commit/65f4fad))
  +* **service-worker:** don't crash if SW not supported ([b9a91a5](https://github.com/angular/angular/commit/b9a91a5))
  +* **service-worker:** send initialization signal from the application ([3fbcde9](https://github.com/angular/angular/commit/3fbcde9))
  +* **service-worker:** use relative path for ngsw.json ([f582620](https://github.com/angular/angular/commit/f582620))
  +
  +
  +
  <a name="5.0.5"></a>
  ## [5.0.5](https://github.com/angular/angular/compare/5.0.4...5.0.5) (2017-12-01)
  