Partial work towards #30

A mega-PR that includes a whole bunch of changes related to intelligent charting (#30):

1. Added analysis module for analyzing JSON, which uses heuristics currently to detect common types.
2. Added interface for charts, which enables generation, perturbation, serialization, and rendering of chart options.
3. Added implementation for `PieChartOptions` based on NVD3.

Once thoroughly tested / debugged, this is expected to become the pattern for other chart types (line, bar, etc.).

Review by @joneshf 
Can these with the single constructor be `newtype`s or are you planning on having multiple constructors in the future?