Infinite Loop when minuteStep or secondStep props are assigned the value "0"

[rajatvijay]

The code at: https://github.com/react-component/time-picker/blob/master/src/Panel.jsx#L13

goes into infinite loop when the value of step is 0.

This is not a bug per se but gives a bad user experience and tracking it down can be non-trivial, mostly for beginners.

One solution that I have is to warn the user when he/she provides "0" value and not let the code go into the loop.

Let me know if I can give a PR for this