Add notes on enabling Travis CI for created repo

[Jiansen]

As promised in #365 , adding notes on enabling Travis CI for a generated app.

Demo

• Demo Repo
• Travis Build

Effects of Change

In the generated app, users will see the note under the Continuous Integration section.

Local verification

In a development branch, run npm run create-react-app my-app and check the README.md in the generated app (my-app).

Note

Build 3 encounters the following error on the Node 4 test. As the Node 6 build succeeds, the failure shall not be related to CRA.

> [email protected] test /home/travis/build/Jiansen/CRA-Travis-Demo
> react-scripts test --env=jsdom
module.js:327
    throw err;
    ^
Error: Cannot find module 'lru-cache'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/home/travis/build/Jiansen/CRA-Travis-Demo/node_modules/react-scripts/node_modules/cross-spawn/lib/parse.js:4:11)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Module.require (module.js:353:17)
npm ERR! Test failed.  See above for more details.

[Jiansen]

Update:

The same issue is reported in #676 and is fixed with 0.4.3.

No change is required to the proposed .travis.yml file.

[ayrton]

This is actually not necessary as travis will add this by default

[Jiansen]

Thanks @ayrton , I removed CI=true in updated commit. Also I added back node 4 tests as the issue is fixed in the new version

[gaearon]

Thanks!