document the onChangeComplete delay and make it configurable

I couldn't find any explanation in the documentation as to what `onChangeComplete` actually does. The [code](https://github.com/casesandberg/react-color/blob/7ee60d845e5d5e11e4f6ecb895b2d9755c59d09d/src/components/common/ColorWrap.js#L30) reveals that it is a hardcoded debounce with 100ms.

I suggest:

1. Document the behavior
2. Make the 100ms configurable

Start with src/components/common/ColorWrap.js at the linked debounce implementation and inspect how onChangeComplete is exposed and invoked. Find the project's documentation entry point for the component, document the callback behavior and delay, and make the delay configurable. Done means the documentation reflects the behavior and the hardcoded 100ms value can be configured.

Written by the indexing model from the issue text.