progress components don't cancel setTimeouts when they unmount

[matgr1]

just looking through the code (and based on what I'm seeing while running), componentDidMount for at least circula-progress and linear-progress don't cancel the setTimeouts that they do... which means whenever you add a progress component this will be looping forever

[chrismcv]

something like this might be a nice pattern
https://github.com/Khan/react-components/blob/master/js/set-interval-mixin.jsx