Upgrade React version

[webwizart]

The demo dapp is still using old react lifecycles

https://reactjs.org/docs/react-component.html

Note:
These methods are considered legacy and you should avoid them in new code:
UNSAFE_componentWillMount()

Note:
This lifecycle was previously named componentWillReceiveProps. That name will continue to work until version 17. Use the rename-unsafe-lifecycles codemod to automatically update your components.

[moxiegirl]

@webwizart Thank you for the issue. Do you have any interest in providing a PR for this? We would really appreciate that.