Bump es6-promise from 4.2.2 to 4.2.4

Bumps [es6-promise](https://github.com/stefanpenner/es6-promise) from 4.2.2 to 4.2.4.
- [Changelog](https://github.com/stefanpenner/es6-promise/blob/master/CHANGELOG.md)
- [Commits](https://github.com/stefanpenner/es6-promise/compare/v4.2.2...v4.2.4)