forked from dk8996's block: D3.js Gantt Chart, example 3
Modified http://d3js.org/d3.v4.min.js to a secure url
Modified http://d3js.org/d3-time-format.min.js to a secure url
https://d3js.org/d3.v4.min.js
https://d3js.org/d3-time.v1.min.js
https://d3js.org/d3-time-format.min.js