Fix Travis build matrix for stable13

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Fix recipients rending of sent messages

Migrate away from some global js dependencies

Signed-off-by: Jan-Christoph Borchardt <hey@jancborchardt.net>

Migrate to a more sophisticated HTML to text lib

Release 0.7.7

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Bump sinon from 4.1.3 to 4.1.4

Bumps [sinon](https://github.com/sinonjs/sinon) from 4.1.3 to 4.1.4.
- [Release notes](https://github.com/sinonjs/sinon/releases)
- [Changelog](https://github.com/sinonjs/sinon/blob/master/History.md)
- [Commits](https://github.com/sinonjs/sinon/compare/v4.1.3...v4.1.4)

* Remove hacky server-side label mangling
* Detect sent folder on the client-side
* Append '& others' in case there is more than one recipient

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Bump phpunit/phpunit from 5.7.25 to 5.7.26

Make account settings editable

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Bump karma from 1.7.1 to 2.0.0

Bump es6-promise from 4.1.1 to 4.2.2

Bumps [karma](https://github.com/karma-runner/karma) from 1.7.1 to 2.0.0.
- [Release notes](https://github.com/karma-runner/karma/releases/tag/v2.0.0)
- [Changelog](https://github.com/karma-runner/karma/blob/master/CHANGELOG.md)
- [Commits](https://github.com/karma-runner/karma/compare/v1.7.1...v2.0.0)