Bump deps / Use del instead of gulp-clean

* Updated dependencies and devDependencies
* Replaced [gulp-clean](https://github.com/peter-vilja/gulp-clean) with [del](https://github.com/sindresorhus/del), because [gulp-clean is deprecated](https://github.com/peter-vilja/gulp-clean/commit/66b1d396fd612b886de096f087a1f7d2dbcb7a62)