This demonstrates Issue #108 in React-Waypoint.

1. Clone this repository
2. Run npm install from the root directory of the repo
3. Open index.html in your browser
4. Scroll around with the console open

The grey square represents the bottom 20% of the viewport. In this example, the scrollableAncestor is the window, meaning that the boundaries of React Waypoint will be the viewport boundaries.

However, topOffset has been specified as 80%, meaning that the top boundary has been scooted down by that much. This means that only the bottom 80% of the viewport will be the area in which waypoints are considered "inside," which will affect when the enter and leave events are triggered.