Treat warnings due to React v15.5

[ThomasJuster]

Warning: ReactSpinner: React.createClass is deprecated and will be removed in version 16. Use plain JavaScript classes instead. If you're not yet ready to migrate, create-react-class is available on npm as a drop-in replacement.

[ThomasJuster]

use createReactClass from pkg 'create-react-class'
Also use the prop-types package

[captDaylight]

hey everyone, I published my fork what I have at react-tiny-spin. I'll maintain it from there :)

[mccambridge]

@captDaylight your docs still instruct users to import react-spin ;)

[captDaylight]

@mccambridge ha, thanks, just update it ! and I added issues to the repo

[techrah]

If you are getting PropTypes warnings, try react-spinjs-fix