Test Node 8 on Travis

[gaearon]

We still test Node 7 on AppVeyor

[gaearon]

Um, this doesn't look amazing 😞

> fsevents@1.1.2 install /tmp/tmp.nEJmaLIQL1/test-app/node_modules/fsevents
> node install
npm ERR! Cannot read property 'type' of undefined

[gaearon]

Seems like this error is npm@5.0.3 bug npm/npm#16812.
Trying to force 5.0.4+ with my non-existent bash skills.

[gaearon]

Heh. Seems like no chance to run with npm@5:

> @ build C:\projects\create-react-app-a3khu
> node packages/react-scripts/scripts/build.js
module.js:472
throw err;
^
Error: Cannot find module 'html-webpack-plugin'
at Function.Module._resolveFilename (module.js:470:15)
at Function.Module._load (module.js:418:25)
at Module.require (module.js:498:17)
at require (internal/module.js:20:19)
at Object.<anonymous> (C:\projects\create-react-app-a3khu\packages\react-scripts\config\webpack.config.prod.js:16:27)
at Module._compile (module.js:571:32)
at Object.Module._extensions..js (module.js:580:10)
at Module.load (module.js:488:32)
at tryModuleLoad (module.js:447:12)
at Function.Module._load (module.js:439:3)
npm ERR! Windows_NT 10.0.14393

I'll try to pin it at 4.x so that we can at least test Node 8 alone.

[Timer]

Was there a specific reason we don't test Node 8 on AppVeyor?

[gaearon]

I don't want to make CI time slower. So I'd rather test two versions here and two versions there. This doesn't catch everything but that's the tradeoff.