Acorn at version 7.0.0

When I installed the latest acorn-node (2.0.1), I get acorn 7.4.1 with it:

```
{
"name": "acorn-node",
"description": "the acorn javascript parser, preloaded with plugins for syntax parity with recent node versions",
"version": "2.0.1",
"author": "Renée Kooi ",
"bugs": {
"url": "https://github.com/browserify/acorn-node/issues"
},
"dependencies": {
"acorn": "^7.0.0",
"acorn-walk": "^7.0.0",
"xtend": "^4.0.2"
},
```

Any change of updating the dependencies? Acorn 8 supports JS syntax that would be useful.