Revert "Update highcharts-rails."
Revert "Update highcharts-rails."

This reverts commit 6d9459d85325ba8290adcfe947b30b88662c2d6d.

bmarkons/ruby-bench-web,klgilbert/ruby-bench-web,ruby-bench/ruby-bench-web,ruby-bench/ruby-bench-web,klgilbert/ruby-bench-web,bmarkons/ruby-bench-web,bmarkons/ruby-bench-web,ruby-bench/ruby-bench-web,klgilbert/ruby-bench-web,treble37/ruby-bench-web,treble37/ruby-bench-web,treble37/ruby-bench-web