* rename state to value in slate core, as deprecation
* rename all references to state to value in slate core
* migrate slate-base64-serializer
* migrate slate-html-serializer
* migrate slate-hyperscript
* migrate slate-plain-serializer
* migrate slate-prop-types
* migrate slate-simulator
* fix change.setState compat
* deprecate references to state in slate-react
* remove all references to state in slate-react
* remove `value` and `schema` from props to all components
* fix default renderPlaceholder
* fix tests
* update examples
* update walkthroughs
* update guides
* update reference
* remove data from event handler signatures
* standardize known transfer types
* add setEventTransfer to docs
* update examples, fix drag/drop
* fix tests and draggable attribute setting
* Allow React 16 in peerDeps and use it for dev
* Make tests pass with React 16
Changes are cosmetic:
- React 16 no longer adds a trailing `;` to `style` attributes
- React 16 outputs `0` and not `0px` for sizes in `style`