Removes resetMin() for New Children

As per this issue I've removed the resetMin() call in componentWillReceiveProps. This is a fix for the use case where you want to dynamically add children without having the scroll reset. There is (to me) not much need for that to happen in cWRP. If you relied on that function call for some reason, it's trivial to add it back. But feel free to open an issue and we can discuss that further.

Big thanks to @MelMepham for her help with this PR.