Feature/improve react tutorial

[henriquealbert]

• [x] Update Meteor and dependencies for each step
• [x] Update Cordova
• [x] Make sure that the web app works
• [x] Make sure that the Cordova app works - test on iOS and Android
• [x] fix GraphQL tutorial
• [x] Add new step on the tutorial to show how to do social login with Github
• [x] Improve the docs, explaining better and improving grammar

[CLAassistant]

All committers have signed the CLA.

[fredmaiaarantes]

LGTM. Well done!