Update readme
Update readme

The documentation needed some refreshing in order to make it more readable and easy.

1. Minimized length of wording to communicate the message. 
2. Removed example code snippet (since they'll see the contents of that example js when they view the boilerplate-embedded JavaScript code).
3. Improved various grammar
yamafaktory/babel-react-rollup-starter,yamafaktory/babel-react-rollup-starter