Migrate d3js to v4 and correct d3js visualisations i.e. bug 3.20. Breadcrumb navigation for the language treemap has been improved
NOTE
====
This project's specs depend on puppet core, and thus they require the
`puppetlabs_spec_helper` project. For more information please see the README
in that project, which can be found here: [puppetlabs spec
helper](https://github.com/puppetlabs/puppetlabs_spec_helper)