Visualization updates

# New in v3.0.1

* `Keen.Metric` now supports `chartOptions.prefix`, `chartOptions.suffix`, and has more stable `colors` handling.
* Grouped interval responses are presented with a multi-line chart now.
* Changed `chartType: "datatable"` to `table`. `datatable` was left behind from an internal project, but breaks the naming pattern we want to establish with underlying libraries.

Resolves #72, #76, #80, #82, #85, #86, #87