Selected date does not update properly when transformed somehow outside React-Calendar

[wojtekmaj]

There is a specific case explained in #27 which causes React-Calendar to misbehave. If the date returned in onChange callback is not what ends up in value prop (e.g. is expanded to a full week like described), React-Calendar will fail to update the value for the second time if the same date is clicked.

This is caused by React-Calendar:

• Assuming the value in props is the same as in state, and comparing values of old and new props in componentWillReceiveProps
• Calling onChange before React-Calendar updates itself