Bump jetty9.version from 9.4.17.v20190418 to 9.4.18.v20190429 (#1431)
Bump jetty9.version from 9.4.17.v20190418 to 9.4.18.v20190429 (#1431)

Bumps `jetty9.version` from 9.4.17.v20190418 to 9.4.18.v20190429.

Updates `jetty-server` from 9.4.17.v20190418 to 9.4.18.v20190429
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.17.v20190418...jetty-9.4.18.v20190429)

Updates `jetty-client` from 9.4.17.v20190418 to 9.4.18.v20190429
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.17.v20190418...jetty-9.4.18.v20190429)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
dropwizard/metrics,dropwizard/metrics,dropwizard/metrics