Based on cmdoptesc's [map timeline example](http://bl.ocks.org/cmdoptesc/fc0e318ce7992bed7ca8). Slider adapted from Mike Bostock's [drag slider](https://bl.ocks.org/mbostock/6452972).

Related examples:
- [Date slider](https://bl.ocks.org/officeofjane/b3f6a4f89a54fb193265b5c05659e17b)
- [Date slider - filtering data](http://bl.ocks.org/officeofjane/9b9e606e9876e34385cc4aeab188ed73)