Major rewrite

New format has two main functions:
- highchartsOutput:
  - Option to specify which js files to load
- renderHighcharts:
  - directly injects the evaluated expr into the highcharts function call
  - specify any highcharts paramter in a list structure that can be converted to JSON format

Main benefit is that this is infinitely flexible.  Main drawback is that the user must become familar with the Highcharts API.

Added two new functions:
- JSONify: Make a dataframe into a JSON object
- getHighchartsColors: returns the default Highcharts colors as of version 4.0.3