This example shows how you can set up tick marks to be a fixed density rather than a fixed number of tick marks. This is useful for implementing visualizations that can be resized by the user.
Derived from
forked from curran's block: Density-based Ticks
Modified http://d3js.org/d3.v3.min.js to a secure url
https://d3js.org/d3.v3.min.js