Update flux-chat example to React 0.12.0

* Update React to 0.12.0
* Switch use of deprecated "merge" and "copyProperties" to "Object.assign"
* Switch to "render" from "renderComponent"
* Other dependency updates
Update flux-todomvc example to React 0.12.0

* Update React to 0.12.0
* Switch use of deprecated "merge" and "copyProperties" to "Object.assign"
* Switch to "render" from "renderComponent"
* Other dependency updates
Update "TodoList.md" for React 0.12.0 changes

* Removed @jsx docblock
* Switch use of deprecated "merge" and "copyProperties" to "Object.assign"
* Switch to "render" from "renderComponent"