* Rewrite "adding React to existing app"
Fixes#988
* Some copy
* typo
* Update babel instructions
* Update umd link
* Add prod minification section
* Show "button" example in several targets
* wip
* More
* More
* tweak
* yas
* Multi root tip
* moaar
* alot
* Tweak links
* Explain better
* better lead
* tweaks
* tweaks
* wording
* More reassuring tone
* Grammar
* wording
* feedback from readers
* Use id, not class
* More nits
* Re-add a useful section
* Break out Installation into top-level doc section
* Update navigation (prev/next, nav tree)
- Move Installation section to top
- Add next/prev to install pages
* add links to other install options from try react page
* fix markdown link
* Clarify that Quick Start and Install are optional "next steps"
* Add top-level CDN page
This is useful for Codepen and other Unpkg-y setups
* Add link to Tutorial from Try React
* Update CRA link in tutorial
* Make Try React subheader a proper sentence
* Add "minimal"
* Explain local dev setup is more work than Codepen etc
* Fix typos
* Add : between headings
* add note that CRA is not lightweight
* fix typo
* Update add-react-to-a-new-app.md
* Update add-react-to-a-new-app.md
* Remove the Bower note
* Update try-react.md
* Tweak wording
* Use direct link
