The PHP version graph is weird for dates without installation data

See https://packagist.org/packages/behat/mink-selenium2-driver/php-stats#1.5 for an example

For dates without data, the charts shows all the versions (having data on some other points) with an equal share. This can be quite confusing when looking at the chart.

Start by reproducing the PHP version chart at the linked Packagist example and trace the code that prepares and renders version data for dates without installations. The issue is done when those dates no longer show every version with an equal share, with coverage for the missing-data case.

Written by the indexing model from the issue text.