Add Extraction Analysis and Table Visualization

This PR provides a class similar to `Metric`, `Series`, and `Funnel`, called `Extraction` that performs an [extraction analysis](https://keen.io/docs/data-analysis/extractions/). The `Extraction` class's default visualization is a `Table`, which is also included in this PR.

The `Table` generates an HTML table from an array of Javascript objects. It does not currently support nested objects.