This commit documents Node.js compatibility for function rest
parameters. This mainly depends on V8 but I tracked the relevant Node
versions, commits and PRs.

Note that I used `4` for the version of the flag addition because `3`
corresponds to the io.js fork and is not recognized as a valid `nodejs`
version by the linter.

Flagged support (io.js 3.0.0, V8 4.4):

- [Node.js changelog entry for version 3.0.0](https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_IOJS.md#2015-08-04-version-300-rvagg)
- [Pull Request](nodejs/node#2022)
- [Commit, with anchor to relevant line](nodejs/node@70d1f32f56#diff-b2e04de0d939630d882245c2243e7e47R200)

Stable support (Node.js 6.0.0, V8 4.7):

- [Node.js changelog entry for version 6.0.0](https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_V6.md#2016-04-26-version-600-current-jasnell)
- [Pull Request](nodejs/node#4106)
- [Commit, with anchor to relevant line](nodejs/node@8a43a3d#diff-b2e04de0d939630d882245c2243e7e47R217)

Flag removal (Node.js 6.0.0, V8 4.9):
- [Node.js changelog entry for version 6.0.0](https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_V6.md#2016-04-26-version-600-current-jasnell)
- [Pull Request](nodejs/node#4722)
- [Commit, with anchor to relevant line](nodejs/node@069e02a#diff-b2e04de0d939630d882245c2243e7e47L221)