V3

[rwieruch]

New Chapters

• adds ES6 class chapter
• adds ES6 modules chapter
• adds general code organization chapter
• adds React ref chapter
• adds all lifecycle methods
• adds PropType chapter
• adds setState chapter
• adds taming the state chapter
• adds Hot Module Reloading
• adds eject chapter

General

• improves wordings and extends explanations
• removes code outcomes after each chapter, but adds link to commit in repository
• splits up overarching 4 chapters into 6 chapters
• elaborates learning path in the end of the book