Upgrade NodeJS
Upgrade NodeJS

```
engines.node (package.json): 6.14.2
engines.npm (package.json): unspecified (use default)
**WARNING** Node version in .nvmrc ignored in favor of 'engines' field in package.json
**ERROR** Unable to install node: no match found for 6.14.2 in
[6.16.0 6.17.0 8.15.0 8.15.1 10.15.2 10.15.3 11.10.1
11.12.0]
```

alphagov/spotlight,alphagov/spotlight,alphagov/spotlight