Bump ical.js from 1.3.0 to 1.4.0

Bumps [ical.js](https://github.com/mozilla-comm/ical.js) from 1.3.0 to 1.4.0.
- [Release notes](https://github.com/mozilla-comm/ical.js/releases)
- [Changelog](https://github.com/mozilla-comm/ical.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mozilla-comm/ical.js/compare/v1.3.0...v1.4.0

)

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