[WIP] change and rearrange the README a bit.

* reword some sentences 
* move most of the justification for the plugin to the bottom.
* Remove some seemingly duplicate information.

Please do not merge this until it has been reviewed by someone else.
I likely misstated or missed things.
I do know some projects have accepted a composer.json so i wrote that many won't . I'm just gonna change it to 'Most developers will not"