Added d3 and nvd3.js, added sample combo chart
code cleanup and axis differentiation
new controller for stats ajax,

method for course response times
group results by response date and show count
use d3 datum format (x,y) and update graph

pretty cool overall response to response by date graph, need to figure
out how to change y coord when removing line
explain the graph
added nvd3 necessary bundles
swap responses and totals so totals shows as line
Merge pull request #53 from ucdavis/SRK-courseeval-graph

Course detail page shows graph of response counts