Update dependency rollup to v1.18.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
rollup	devDependencies	minor	1.17.0 -> 1.18.0

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Release Notes

rollup/rollup

### [`v1.18.0`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​1180) [Compare Source](https://togithub.com/rollup/rollup/compare/v1.17.0...v1.18.0) _2019-08-01_ ##### Features - Add `externalLiveBindings: false` option to optimize code when live bindings are not needed ([#​3010](https://togithub.com/rollup/rollup/issues/3010)) ##### Pull Requests - [#​2997](https://togithub.com/rollup/rollup/pull/2997): Integrate coverage into CI setup ([@​lukastaegert](https://togithub.com/lukastaegert)) - [#​2998](https://togithub.com/rollup/rollup/pull/2998): Update readme badges ([@​lukastaegert](https://togithub.com/lukastaegert)) - [#​3010](https://togithub.com/rollup/rollup/pull/3010): Add option to prevent code for external live bindings ([@​lukastaegert](https://togithub.com/lukastaegert))

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