[5.6] Adds manual migration steps

[tylersmalley]

[tylersmalley]

Jenkins, test it

[tylersmalley]

Build failure is also happening on the 5.6 branch:

14:44:44 Error: Cannot find module '../src/babel-register'
14:44:44     at Function.Module._resolveFilename (module.js:469:15)
14:44:44     at Function.Module._load (module.js:417:25)
14:44:44     at Module.require (module.js:497:17)
14:44:44     at require (internal/module.js:20:19)
14:44:44     at Object.<anonymous> (/var/lib/jenkins/workspace/elastic+kibana+5.6+multijob-intake/scripts/eslint.js:1:63)
14:44:44     at Module._compile (module.js:570:32)
14:44:44     at Object.Module._extensions..js (module.js:579:10)
14:44:44     at Module.load (module.js:487:32)
14:44:44     at tryModuleLoad (module.js:446:12)
14:44:44     at Function.Module._load (module.js:438:3)