I modified your code slightly to use the rCharts syntax. You will need to install the dev branch of rCharts from github to run this application.
devtools::install_github("rCharts", "ramnathv", ref = "dev")
shiny::runGist('7074303')
I made three changes to your code:
library(rHighcharts) with library(rCharts) in both ui.R and server.Ra <- Highcharts$new() to make use of rCharts class.renderChart with renderChart2 which is a modified version of renderChart and will eventually replace it.