TodoMVC demo bugs

[chenglou]

Repro:

• Go to https://codesandbox.io/embed/2pk8l7n7kn
• Type "asd" really quickly
• See that things unmount immediately without transition

Nice lib! =D

[drcmda]

Thanks for the all the inspiration and the impact that your work had on the React eco system at large!

Transition is such a hard piece of work, i saw how much effort was put into it in react-motion.

I'll go hunting ...

[drcmda]

fixed in 4.0.2.