ported rCharts plotting library, possible add for chendaniely/ebola#3 and chendaniely/ebola#5

I added two tabs to the Shiny app. Both render plots using rCharts (chendaniely/ebola#5). You need to load the [dev version of rCharts](https://github.com/ramnathv/rCharts/tree/dev) into the namespace for this to work. For some reason, I can't seem to include the google-analytics script so I commented that line out:

[Rickshaw](http://code.shutterstock.com/rickshaw/). An interactive line graph plotting cases and deaths in absolute time (chendaniely/ebola#3). Features include hover details and a slider bar to zoom in on selected time periods, but  I can't get the latter to work properly in the Shiny application. This is a [known issue in rCharts](https://github.com/ramnathv/rCharts/issues/200).

![screenshot 2014-10-19 03 10 27](https://cloud.githubusercontent.com/assets/6497572/4692378/b6ed3732-575f-11e4-819a-c71b0b78fbc4.png)

[NVD3](http://nvd3.org/examples/multiBar.html). Stacked bar plots of cases and deaths for the most recently updated figures from each country. Features include transitions from grouped to stacked and coordinate flipping.

![screenshot 2014-10-19 03 10 40](https://cloud.githubusercontent.com/assets/6497572/4692376/af68064a-575f-11e4-91d3-9190c0daedbc.png)

**TODO**

* fix slider on Rickshaw
* add reactive data table to bottom of Rickshaw tab
* make sidepanel narrower to give more room for graphs
* add axis labels to graphs