Bump websocket-extensions from 0.1.3 to 0.1.4 in /mailbag/client

Bumps [websocket-extensions](https://github.com/faye/websocket-extensions-node) from 0.1.3 to 0.1.4.
- [Release notes](https://github.com/faye/websocket-extensions-node/releases)
- [Changelog](https://github.com/faye/websocket-extensions-node/blob/master/CHANGELOG.md)
- [Commits](faye/websocket-extensions-node@0.1.3...0.1.4)

Signed-off-by: dependabot[bot] <support@github.com>