Bump shelljs and pre-push

Removes [shelljs](https://github.com/shelljs/shelljs). It's no longer used after updating ancestor dependency [pre-push](https://github.com/dflourusso/pre-push). These dependencies need to be updated together.


Removes `shelljs`

Updates `pre-push` from 0.1.1 to 0.1.4
- [Changelog](https://github.com/dflourusso/pre-push/blob/master/CHANGELOG.md)
- [Commits](https://github.com/dflourusso/pre-push/commits)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: pre-push
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>