chore(package): update rollup to version 0.60.7

[christophercr]

Closes #437

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

Does this PR introduce a breaking change?

[ ] Yes
[X] No

[coveralls]

Coverage remained the same at 94.247% when pulling ca83e97 on greenkeeper/rollup-0.60.7 into 0cd6de1 on master.