Bump coffeescript from 2.3.2 to 2.6.1

Bumps [coffeescript](https://github.com/jashkenas/coffeescript) from 2.3.2 to 2.6.1.
- [Release notes](https://github.com/jashkenas/coffeescript/releases)
- [Commits](jashkenas/coffeescript@2.3.2...2.6.1)

---
updated-dependencies:
- dependency-name: coffeescript
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]