static bezier(
    x1: number,
    y1: number,
    x2: number,
    y2: number
  ): (t: number) => number {
    const _bezier = require('bezier');
    return _bezier(x1, y1, x2, y2);
  }
Provides a cubic bezier curve, equivalent to CSS Transitions'
`transition-timing-function`.

A useful tool to visualize cubic bezier curves can be found at
http://cubic-bezier.com/