Refactored charting libraries to extract out getJSON call to main.js, now decoupled from actual charting library. Charts no longer need to maintain a cached data since we dedicate a chart to each date range, and keep track of if updated from within main.js. Also added loading gif.
added nvd3 charting functionality, commented out still sticking to highcharts. moved vendor javascript includes from app.rb to environments.rb. Modified populateZeroForMissingDates from both highcharts and nvd3 to populate max date range instead of individually for each pollen count. this was because d3 requires matching array length for data sets.